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Quantum Computing News and Reports off the Wire. **You’ll find the latest news from our most reliable sources, here. The news, uncategorized, awaiting our review. Get it first. Because Quantum is Coming. Qubit.

- AI Expo Showcases Lab’s Diversity of Machine Learning and Deep Learning ResearchAugust 16, 2019 — ORNL hosted its first AI Expo on Monday, July 29 to showcase the diverse portfolio of AI research taking place across the Laboratory. From materials science to healthcare to national security, AI has tremendous potential to accelerate breakthroughs across all of ORNL’s research domains. The Expo was organized into three presentation sessions and two poster sessions and was designed to: strengthen and share information across the Laboratory’s AI community of practice; showcase ORNL’s AI capabilities; highlight outstanding science and engineering based on AI; and highlight potential needs addressable with AI. In all, 12 speakers elaborated on their collaborative research and researchers presented 50 posters detailing a wide spectrum of AI ... READ MORE
- For superconductors, discovery comes from disorderDiscovered more than 100 years ago, superconductivity continues to captivate scientists who seek to develop components for highly efficient energy transmission, ultrafast electronics or quantum bits for next-generation computation. However, determining what causes substances to become—or stop being—superconductors remains a central question in finding new candidates for this special class of materials. In potential superconductors, […] The post For superconductors, discovery comes from disorder appeared first on Science Bulletin. ... READ MORE
- Researchers demonstrate three-dimensional quantum hall effect for the first timeThe quantum Hall effect (QHE), which was previously known for two-dimensional (2D) systems, was predicted to be possible for three-dimensional (3D) systems by Bertrand Halperin in 1987: Now it has been demonstrated. ... READ MORE
- Newfound superconductor material could be the ‘silicon of quantum computers’A potentially useful material for building quantum computers has been unearthed at the National Institute of Standards and Technology (NIST), whose scientists have found a superconductor that could sidestep one of the primary obstacles standing in the way of effective quantum logic circuits. Newly discovered properties in the compound uranium ditelluride, or UTe2, show that […] The post Newfound superconductor material could be the ‘silicon of quantum computers’ appeared first on Science Bulletin. ... READ MORE
- Racing toward Absolute ZeroA lab at the University of Cambridge is looking for materials that have weird quantum properties at the coldest temperatures possible -- Read more on ScientificAmerican.com ... READ MORE
- How to observe and quantify quantum-discord states via correlationsAuthor(s): Matthew A. Hunt, Igor V. Lerner, Igor V. Yurkevich, and Yuval GefenQuantum correlations between parts of a composite system most clearly reveal themselves through entanglement. Designing, maintaining, and controlling entangled systems is very demanding, which raises the stakes for understanding the efficacy of entanglement-free, yet quantum correlations, exemplifie...[Phys. Rev. A 100, 022321] Published Fri Aug 16, 2019 ... READ MORE
- Semiquantum key distribution with high quantum noise toleranceAuthor(s): Omar Amer and Walter O. KrawecSemiquantum key distribution protocols are designed to allow two parties to establish a shared secret key, secure against an all-powerful adversary, even when one of the users is restricted to measuring and preparing quantum states in one single basis. While interesting from a theoretical standpoint...[Phys. Rev. A 100, 022319] Published Fri Aug 16, 2019 ... READ MORE
- Hotly debated carbon ring allotrope reveals its structure
- Victor Batista named the Huffman Professor of ChemistryBatista focuses his research on the development of rigorous and practical methods for simulations of quantum processes in complex systems ... READ MORE
- Newfound superconductor material could be the ‘silicon of quantum computers’Newly discovered properties in the compound uranium ditelluride show that it could prove highly resistant to one of the nemeses of quantum computer development -- the difficulty with making such a computer's memory storage switches, called qubits, function long enough to finish a computation before losing the delicate physical relationship that allows them to operate as a group. This relationship, called quantum coherence, is hard to maintain because of disturbances from the surrounding world. ... READ MORE
- Researchers Discover What Could Be a New Substrate for Building “Topological” QubitsUranium ditelluride could one day help in the construction of quantum computers ... READ MORE
- Scientists discover new state of matterA team of physicists has uncovered a new state of matter—a breakthrough that offers promise for increasing storage capabilities in electronic devices and enhancing quantum computing. ... READ MORE
- Quantum system virtually cooled to half of its actual temperaturePhysicists have developed a quantum simulation method that can "virtually cool" an experimental quantum system to a fraction of its actual temperature. The method could potentially allow access to extremely low-temperature phenomena, such as unusual forms of superconductivity, that have never been observed before. The simulation involves preparing multiple copies of the system's quantum state, interfering the states, and making measurements on each copy, which ultimately yields a simulated measurement on the same system at a lower temperature. ... READ MORE
- Shining Light Through Bleach Creates Fluorescent Quantum DefectsUsing household bleach and light, MIT researchers have created fluorescent quantum defects in carbon nanotubes. The defects can be synthesized quickly and at large scale, the researchers said. The researchers treated carbon nanotubes at room temperature with NaClO (bleach) and irradiated the nanotubes with ultraviolet light for less than a minute to achieve optimized oxygen-doping. The doping efficiency was controlled by varying surfactant concentration and type, NaClO concentration, and irradiation dose. Submerging a carbon nanotube in bleach produces an oxygen atom (red) that reacts with the carbon atoms (black) of the nanotube, forming a fluorescent quantum defect when irradiated with ultraviolet light. Courtesy of the ... READ MORE
- Quantum-assisted telescope arraysAuthor(s): E. T. Khabiboulline, J. Borregaard, K. De Greve, and M. D. LukinQuantum networks provide a platform for astronomical interferometers capable of imaging faint stellar objects. In a recent work [E. T. Khabiboulline
*et al.*, Phys. Rev. Lett.**123**, 070504 (2019)], we presented a protocol that circumvents transmission losses with efficient use of quantum resources and...[Phys. Rev. A 100, 022316] Published Thu Aug 15, 2019 ... READ MORE - Synopsis: Quantum Teleportation Now Comes in 3DThe first experiment to teleport qutrits rather than qubits paves the way to teleporting the complete quantum state of a particle.[Physics] Published Thu Aug 15, 2019 ... READ MORE
- Light can scatter from light, CERN physicists confirmThe quantum electrodynamic process of photon–photon scattering has for the first time been confirmed experimentally to a high degree of certainty. CERN’s ATLAS collaboration, which involves hundreds of physicists from around the world, made the breakthrough after analysing a large dataset of candidate scattering events using a neural network. Their discovery could fuel new research into a variety of theories beyond the Standard Model of particle physics. In classical electrodynamics, photons cannot interact with each other because they have no charge. At the same time, however, quantum electrodynamics predicts that two photons can scatter off each other by exchanging virtual charged fermions or W bosons. Some theorized extensions to the Standard Model predict that these scattering events are ... READ MORE
- Northwestern professor receives DOE funding for quantum information science researchMichael R. Wasielewski, Clare Hamilton Hall Professor of Chemistry at Northwestern University and Executive Director of the Institute for Sustainability and Energy, will receive $1.5 million over three years from the Department of Energy (DOE) for research toward the development of new Quantum Information Science (QIS). His award is a part of a total of $37 million in DOE funding granted to some 20 projects selected through competitive peer review for targeted research in materials and chemistry. “The scientific community is on the verge of a revolution in which Quantum Information Science will change the way we live, work, and understand our world. Indeed, QIS may have the opportunity to transform industries, create jobs, and yield great benefits for the ... READ MORE
- Pushing the boundaries of convex optimizationConvex optimization has many applications ranging from operations research and machine learning to quantum information theory. Convex optimization problems, which involve the minimization of a convex function over a convex set, can be approximated in theory to any fixed precision in polynomial time. However, practical algorithms are known only for special cases. Some well-known special cases include linear programming, convex quadratic programming, and convex quadratically-constrained quadratic programming, which are the workhorses of operations research. They are also special cases of semidefinite programming (SDP), which optimizes a linear objective over a set of positive semidefinite matrices. SDP has numerous additional applications such as recommender systems [1] and power systems [2]. An important question is whether it is possible to develop algorithms ... READ MORE
- Schrödinger’s cat with 20 qubitsDead or alive, left-spinning or right-spinning—in the quantum world particles such as the famous analogy of Schrödinger's cat can be all these things at the same time. An international team, including researchers from several leading American universities, together with experts from Forschungszentrum Jülich, have now succeeded in transforming 20 entangled quantum bits into such a state of superposition. The generation of such atomic Schrödinger cat states is regarded as an important step in the development of quantum computers which could outperform classical computers in solving certain tasks. The results were published in Science last Friday. ... READ MORE
- Schrödinger’s cat with 20 qubitsDead or alive, left-spinning or right-spinning -- in the quantum world particles such as the famous analogy of Schrödinger's cat can be all these things at the same time. An international team, together with experts from Forschungszentrum Jülich, have now succeeded in transforming 20 entangled quantum bits into such a state of superposition. The generation of such atomic Schrödinger cat states is regarded as an important step in the development of quantum computers. ... READ MORE
- Graphene paves the way for novel product enabling industrial usersNPL, Chalmers University of Technology and Graphensic, have demonstrated the long-term stability of the epigraphene quantum Hall chip, which represents a key step towards enabling end-users to maintain their own resistance standards ... READ MORE
- Topological photonics offers route to qubit-to-qubit communicationA new toolbox for sophisticated quantum simulators, in which qubits can directly communicate through so-called “topological radio channels”, has been proposed by physicists in Germany and Spain. Researchers led by Alejandro González-Tudela at the Max Planck Institute for Quantum Optics in Garching constructed the theory by transferring the principles of topology from condensed matter to photonics. Topology has become an incredibly influential branch of mathematics in recent years. In geometric terms, it describes how an object can easily be transformed into another object with the same number of holes, without cutting or gluing. In condensed matter, meanwhile, topological materials display similar geometries on the molecular scale, which gives them diverse mechanical and electrical properties. Recent studies have explored how the ... READ MORE
- Continuous-variable entanglement distillation over a pure loss channel with multiple quantum scissorsAuthor(s): Kaushik P. Seshadreesan, Hari Krovi, and Saikat GuhaEntanglement distillation is a key primitive for distributing high-quality entanglement between remote locations. Probabilistic noiseless linear amplification based on the quantum scissors is a candidate for entanglement distillation from noisy continuous-variable (CV) entangled states. Being a non-...[Phys. Rev. A 100, 022315] Published Tue Aug 13, 2019 ... READ MORE
- Supersolidity appears in ultracold atomsOriginally predicted at the end of the 1960s, researchers still can’t say with certainty that they have actually observed the supersolid phase of matter in the laboratory. Physicists in Austria now report that they have found further evidence for this phase in a Bose-Einstein condensate made of erbium atoms. The finding will help advance our understanding of how spontaneous symmetry breaking occurs in quantum systems, they say. It also confirms that ultracold atoms are a powerful test bed in which to study highly non-trivial quantum phenomena. A supersolid is a paradoxical form of matter – it flows without friction (like a superfluid) but its particles are arranged in a crystalline lattice (like a solid). Indeed, it is described as being ... READ MORE
- How do atoms vibrate in graphene nanostructures?In order to understand advanced materials like graphene nanostructures and optimize them for devices in nano-, opto- and quantum-technology it is crucial to understand how phonons—the vibration of atoms in solids—influence the materials' properties. Researchers from the University of Vienna, the Advanced Institute of Science and Technology in Japan, the company JEOL and La Sapienza University in Rome have developed a method capable to measure all phonons existing in a nanostructured material. This is a breakthrough in the analysis of nanoscale functional materials and devices. With this pilot experiment using graphene nanostructures these researchers have shown the uniqueness of their approach, which will be published in the latest issue of Nature. ... READ MORE
- Classification of phases for mixed states via fast dissipative evolutionQuantum 3, 174 (2019).https://doi.org/10.22331/q-2019-08-12-174We propose the following definition of topological quantum phases valid for mixed states: two states are in the same phase if there exists a time independent, fast and local Lindbladian evolution driving one state into the other. The underlying idea, motivated by [1], is that it takes time to create new topological correlations, even with the use of dissipation. We show that it is a good definition in the following sense: (1) It divides the set of states into equivalent classes and it establishes a partial order between those according to their level of ``topological complexity''. (2) It provides a path between any two states belonging to the same phase where observables behave smoothly. We then focus ... READ MORE
- A polar decomposition for quantum channels (with applications to bounding error propagation in quantum circuits)Quantum 3, 173 (2019).https://doi.org/10.22331/q-2019-08-12-173Inevitably, assessing the overall performance of a quantum computer must rely on characterizing some of its elementary constituents and, from this information, formulate a broader statement concerning more complex constructions thereof. However, given the vastitude of possible quantum errors as well as their coherent nature, accurately inferring the quality of composite operations is generally difficult. To navigate through this jumble, we introduce a non-physical simplification of quantum maps that we refer to as the leading Kraus (LK) approximation. The uncluttered parameterization of LK approximated maps naturally suggests the introduction of a unitary-decoherent polar factorization for quantum channels in any dimension. We then leverage this structural dichotomy to bound the evolution -- as circuits grow in depth -- ... READ MORE
- The Non-m-Positive Dimension of a Positive Linear MapQuantum 3, 172 (2019).https://doi.org/10.22331/q-2019-08-12-172We introduce a property of a matrix-valued linear map $Phi$ that we call its ``non-m-positive dimension'' (or ``non-mP dimension'' for short), which measures how large a subspace can be if every quantum state supported on the subspace is non-positive under the action of $I_m otimes Phi$. Equivalently, the non-mP dimension of $Phi$ tells us the maximal number of negative eigenvalues that the adjoint map $I_m otimes Phi^*$ can produce from a positive semidefinite input. We explore the basic properties of this quantity and show that it can be thought of as a measure of how good $Phi$ is at detecting entanglement in quantum states. We derive non-trivial bounds for this quantity for some well-known positive maps of ... READ MORE
- Guaranteed recovery of quantum processes from few measurementsQuantum 3, 171 (2019).https://doi.org/10.22331/q-2019-08-12-171Quantum process tomography is the task of reconstructing unknown quantum channels from measured data. In this work, we introduce compressed sensing-based methods that facilitate the reconstruction of quantum channels of low Kraus rank. Our main contribution is the analysis of a natural measurement model for this task: We assume that data is obtained by sending pure states into the channel and measuring expectation values on the output. Neither ancillary systems nor coherent operations across multiple channel uses are required. Most previous results on compressed process reconstruction reduce the problem to quantum state tomography on the channel's Choi matrix. While this ansatz yields recovery guarantees from an essentially minimal number of measurements, physical implementations of such schemes would ... READ MORE
- Entanglement balance of quantum $(e,2e)$ scattering processesAuthor(s): Konstantin A. Kouzakov, Levan Chotorlishvili, Jonas Wätzel, Jamal Berakdar, and Arthur ErnstThe theory of quantum information constitutes the functional value of the quantum entanglement, i.e., quantum entanglement is essential for high fidelity of quantum protocols, while fundamental physical processes behind the formation of quantum entanglement are less relevant for practical purposes. ...[Phys. Rev. A 100, 022311] Published Mon Aug 12, 2019 ... READ MORE
- Quantum-error-correction-assisted quantum metrology without entanglementAuthor(s): Kok Chuan Tan, S. Omkar, and Hyunseok JeongIn this article we study the role that quantum resources play in quantum-error-correction-assisted quantum metrology (QECQM) schemes. We show that there exist classes of such problems where entanglement is not necessary to retrieve noise-free evolution and Heisenberg scaling in the long time limit. ...[Phys. Rev. A 100, 022312] Published Mon Aug 12, 2019 ... READ MORE
- Steerability detection of an arbitrary two-qubit state via machine learningAuthor(s): Changliang Ren and Changbo ChenQuantum steering is an important nonclassical resource for quantum information processing. However, even though lots of steering criteria exist, it is still very difficult to efficiently determine whether an arbitrary two-qubit state shared by Alice and Bob is steerable or not, because the optimal m...[Phys. Rev. A 100, 022314] Published Mon Aug 12, 2019 ... READ MORE
- Optimal bounds on state transfer under quantum channels with application to spin system engineeringAuthor(s): Wenqiang Zheng, Hengyan Wang, Tao Xin, Xinfang Nie, Dawei Lu, and Jun LiModern applications of quantum control in quantum information science and technology require the precise characterization of quantum states and quantum channels. In particular, high-performance quantum state engineering often demands that quantum states are transferred with optimal efficiency via re...[Phys. Rev. A 100, 022313] Published Mon Aug 12, 2019 ... READ MORE
- Artificial intelligence, quantum computing and the laws of encryptionThe last decade has seen several science and technology breakthroughs. From self-driving cars to 3D-printing, clean energy technologies to artificial.. ... READ MORE
- A single-photon source you can make at homeQuantum computing and quantum cryptography are expected to give much higher capabilities than their classical counterparts. For example, the computation power in a quantum system may grow at a double exponential rate instead of a classical linear rate due to the different nature of the basic unit, the qubit (quantum bit). Entangled particles enable the unbreakable codes for secure communications. The importance of these technologies motivated the U.S. government to legislate the National Quantum Initiative Act, which authorizes $1.2 billion over the following five years for developing quantum information science. Single photons can be an essential qubit source for these applications. To achieve practical usage, the single photons should be in the telecom wavelengths, which range from 1,260-1,675 nanometers, and ... READ MORE
- A single-photon source you can make at homeQuantum computing and quantum cryptography are expected to give much higher capabilities than their classical counterparts. For example, the computation power in a quantum system may grow at a double exponential rate instead of a classical linear rate due to the different nature of the basic unit, the qubit (quantum bit). Entangled particles enable the unbreakable codes for secure communications. The importance of these technologies motivated the U.S. government to legislate the National Quantum Initiative Act, which authorizes $1.2 billion over the following five years for developing quantum information science. Single photons can be an essential qubit source for these applications. To achieve practical usage, the single photons should be in the telecom wavelengths, which range from 1,260-1,675 nanometers, and ... READ MORE
- Quantum computing with semiconductor spinsOpen any textbook on quantum mechanics, and the two-state system of choice is likely to be a spin-½ particle, such as an electron. The corresponding states, spin up and spin down, form the prototypical quantum bit (qubit), and rotations of the spin state constitute the simplest quantum logic gates. Because of their negative charge, electrons can be manipulated with voltages applied to nanoscale electrodes, or gates. And the application of appropriate voltages can confine the electrons to small islands called quantum dots. Twenty years ago Daniel Loss and David DiVincenzo proposed that the spin of a single electron in a semiconductor quantum dot could form not just a model but also a real, physical qubit.1 Their theoretical work predated by four years the first experiments to successfully trap a single electron in a gate-defined quantum dot, and it predated by several more ... READ MORE
- Neuron-inspired electrical model goes quantumAn electrical circuit inspired by the functionality of a neuron can operate in the quantum regime, according to recent models by a team of scientists from Spain and China. The researchers found that the distinct dynamics of information transport through a neuron are preserved when the signal is fully quantized. This merging of brain-function inspired networks and quantum informatics could lead to enhanced computing systems, as well as benefit growing research fields such as quantum machine learning. The idea that information travels through neurons like electrical signals through a circuit is known as the Hodgkin-Huxley model. This was awarded the 1963 Nobel Prize in Medicine and created a strong link between physics and neuroscience. Since then many attempts to improve ... READ MORE
- Quantum Cryptography Needs a RebootToday, it's a boutique security product—but its enabling tech could someday power large-scale quantum computing ... READ MORE
- Focus: Entangling Photon Sources on a Tiny BridgeAuthor(s): Philip BallResearchers entangled a pair of atomic-scale light emitters in a micrometer-scale device, which could potentially be useful for quantum communication and cryptography.[Physics 12, 90] Published Fri Aug 09, 2019 ... READ MORE
- Converting quantum coherence to genuine multipartite entanglement and nonlocalityAuthor(s): Ya Xi, Tinggui Zhang, Zhu-Jun Zheng, Xianqing Li-Jost, and Shao-Ming FeiWe study the relations between quantum coherence and quantum nonlocality, genuine quantum entanglement, and genuine quantum nonlocality. We show that the coherence of a qubit state can be converted to the nonlocality of two-qubit states via incoherent operations. The results are also generalized to ...[Phys. Rev. A 100, 022310] Published Fri Aug 09, 2019 ... READ MORE
- Quantum teleportation, FLASH radiotherapy and the end of electricity from coalResearchers have been raising the bar for quantum teleportation as Susan Curtis explains in this week’s podcast. While standard quantum teleportation has been limited to particles with just two states, the latest results set the technique on a trajectory for teleporting more complicated systems. Also in the news this week, Margaret Harris reveals the conclusions of a study on the possible impact of visa restrictions for start-ups, who hope to attract the most suitable candidates for a highly specialized work force. We get some of the scoop from the American Association of Physicists in Medicine (AAPM) Annual Meeting as Tami Freeman reports back on some of the topics that caught her eye, including FLASH radiotherapy, which uses high dose rates ... READ MORE
- Quantum approach reveals faster protein foldingThe study of protein folding is fundamental in biophysics because it is important for understanding how proteins function in a wide range of biological processes and for investigating diseases like Alzheimer’s and Parkinson’s in which proteins misfold. Thanks to a new quantum approach, researchers in China have now found that proteins could fold much faster than previous calculations suggest. Proteins consist of a long chain of molecules known as amino acids folded into a 3D shape. Researchers have been studying protein folding since the 1950s, and in 1956, two postdocs working at the Carlsberg Laboratory in Copenhagen, John Schellman and Bill Harrington, were the first to discover that protein folding reactions are very fast and often reversible. However, just ... READ MORE
- Preparation of bipartite bound entangled Gaussian states in quantum opticsAuthor(s): Shan Ma, Matthew J. Woolley, Xiaojun Jia, and Jing ZhangThe positivity of the partial transpose is in general only a necessary condition for separability. There exist quantum states that are not separable, but nevertheless are positive under the partial transpose. States of this type are known as bound entangled states, meaning that these states are enta...[Phys. Rev. A 100, 022309] Published Thu Aug 08, 2019 ... READ MORE
- Observation of nonclassical measurement statistics induced by a coherent spin environmentAuthor(s): D. D. Bhaktavatsala Rao, Sen Yang, Stefan Jesenski, Emre Tekin, Florian Kaiser, and Jörg WrachtrupWe demonstrate the role of measurement back action of a coherent spin environment in the dynamics of a spin (qubit) coupled to it, by inducing nonclassical (quantum random walk–like) statistics on its measurement trajectory. We show how the long lifetime of the spin bath correlates with measurements...[Phys. Rev. A 100, 022307] Published Thu Aug 08, 2019 ... READ MORE
- Synopsis: Entangling the Radial Parts of PhotonsCorrelations between the radial position and radial momentum of entangled photons demonstrate the suitability of these properties for quantum information applications. [Physics] Published Thu Aug 08, 2019 ... READ MORE
- Experimental investigation of the nonlocal advantage of quantum coherenceAuthor(s): Zhi-Yong Ding, Huan Yang, Hao Yuan, Dong Wang, Jie Yang, and Liu YeNonlocal advantage of quantum coherence (NAQC) based on coherence complementarity relations is generally viewed as a stronger nonclassical correlation than Bell nonlocality. An arbitrary two-qubit state with NAQC must be an entangled state, which demonstrates that the criterion of NAQC can also be r...[Phys. Rev. A 100, 022308] Published Thu Aug 08, 2019 ... READ MORE
- Breakthrough prize criticized for rewarding ‘failed ideas’Three proponents of “supergravity” – a theory that attempts to unify all the forces of nature – have been awarded with a Special Breakthrough Prize worth $3m. Theorists Sergio Ferrara from the CERN particle-physics lab near Geneva, Daniel Freedman from the Massachusetts Institute of Technology and Stanford University, and Peter van Nieuwenhuizen from Stony Brook University, share the prize for work they carried out in the 1970s that unifies general relativity and supersymmetry. The announcement, however, has been met with derision by some who say that such a high-profile physics prize should not go to a speculative theory that has not been tested experimentally. By the early 1970s, physicists had unified the electromagnetic, weak and strong forces via the now-famous ... READ MORE
- Quantum teleportation moves into the third dimensionPhysicists in China and Austria have shown for the first time they can teleport multi-dimensional states of photons. Carrying out experiments using photons encoded via three spatial states, they say their scheme can be extended to arbitrarily high numbers of dimensions and is a vital step in teleporting the entire quantum state of a particle. The work could also improve technology used in quantum communications and quantum computing. Quantum mechanics forbids the quantum state of one particle from being copied precisely to another particle. But teleportation – the instantaneous transfer of a state between particles separated by a long distance – offers an alternative. The process involves no physical transfer of matter and erases the state of the particle to ... READ MORE
- Unifying the Clifford hierarchy via symmetric matrices over ringsAuthor(s): Narayanan Rengaswamy, Robert Calderbank, and Henry D. PfisterThe Clifford hierarchy of unitary operators is a foundational concept for universal quantum computation. It was introduced to show that universal quantum computation can be realized via quantum teleportation, given access to certain standard resources. While the full structure of the hierarchy is st...[Phys. Rev. A 100, 022304] Published Wed Aug 07, 2019 ... READ MORE
- Improving the performance of twin-field quantum key distributionAuthor(s): Feng-Yu Lu, Zhen-Qiang Yin, Chao-Han Cui, Guan-Jie Fan-Yuan, Rong Wang, Shuang Wang, Wei Chen, De-Yong He, Wei Huang, Bing-Jie Xu, Guang-Can Guo, and Zheng-Fu HanAmong the various versions of the twin-field quantum key distribution (TF-QKD) protocol [M. Lucamarini, Z. Yuan, J. Dynes, and A. Shields, Nature (London)
**557**, 400 (2018)] that can overcome the rate-distance limit, the TF-QKD without phase postselection proposed by Cui*et al.*[Phys. Rev. Appl.**11**, 0...[Phys. Rev. A 100, 022306] Published Wed Aug 07, 2019 ... READ MORE - Visa policies may restrict access to talent for US tech start-upsRestrictions on US work visas may be deterring foreign-born science and engineering PhDs from taking jobs at technology start-ups, depriving new companies of scarce talent. That is the conclusion of researchers at Cornell University and the University of California, San Diego, whose survey of STEM PhD recipients at US universities found that foreign PhDs were 56% less likely than their US peers to accept a job at a start-up, despite expressing more interest in start-ups when they were students and being just as likely to apply to and receive job offers from them. Michael Roach and John Skrentny based their conclusions on a survey of 2324 people who earned PhDs in STEM subjects from US universities between 2010 ... READ MORE
- Robust quantum control against clock noises in multiqubit systemsAuthor(s): Hai-Jin Ding and Re-Bing WuHigh-precision manipulation of multiqubit quantum systems requires strictly clocked and synchronized multichannel control signals. However, practical arbitrary wave-form generators always suffer from random signal jitters and channel latencies that induce nonignorable state or gate operation errors....[Phys. Rev. A 100, 022302] Published Tue Aug 06, 2019 ... READ MORE
- Thick OLEDs can have high light-emitting efficiencies tooResearchers have made high-performance thick organic light-emitting diodes (OLEDs) by combining organic thin films and organic-inorganic perovskite transport layers. The materials, which have the same light-emitting efficiencies as reference thin OLEDs, could be used to make affordable displays and screens that emit the same colour from all viewing angles. OLEDs make use of layers of organic molecules to efficiently convert electricity into light. The organic layers are placed between two electrodes, one of which is usually transparent. They are ideal for applications in next-generation displays and lighting but the problem is that they need to be made as thin as around 100 nm. This is because organic molecules, while being excellent emitters of light, are generally poor conductors. Only such thin layers ... READ MORE
- Clifford recompilation for faster classical simulation of quantum circuitsQuantum 3, 170 (2019).https://doi.org/10.22331/q-2019-08-05-170Simulating quantum circuits classically is an important area of research in quantum information, with applications in computational complexity and validation of quantum devices. One of the state-of-the-art simulators, that of Bravyi et al, utilizes a randomized sparsification technique to approximate the output state of a quantum circuit by a stabilizer sum with a reduced number of terms. In this paper, we describe an improved Monte Carlo algorithm for performing randomized sparsification. This algorithm reduces the runtime of computing the approximate state by the factor $ell/m$, where $ell$ and $m$ are respectively the total and non-Clifford gate counts. The main technique is a circuit recompilation routine based on manipulating exponentiated Pauli operators. The recompilation routine also facilitates numerical ... READ MORE
- Simulating boson sampling in lossy architecturesQuantum 3, 169 (2019).https://doi.org/10.22331/q-2019-08-05-169Photon losses are among the strongest imperfections affecting multi-photon interference. Despite their importance, little is known about their effect on boson sampling experiments. In this work we show that using classical computers, one can efficiently simulate multi-photon interference in all architectures that suffer from an exponential decay of the transmission with the depth of the circuit, such as integrated photonic circuits or optical fibers. We prove that either the depth of the circuit is large enough that it can be simulated by thermal noise with an algorithm running in polynomial time, or it is shallow enough that a tensor network simulation runs in quasi-polynomial time. This result suggests that in order to implement a quantum advantage experiment ... READ MORE
- Tight, robust, and feasible quantum speed limits for open dynamicsQuantum 3, 168 (2019).https://doi.org/10.22331/q-2019-08-05-168Starting from a geometric perspective, we derive a quantum speed limit for arbitrary open quantum evolution, which could be Markovian or non-Markovian, providing a fundamental bound on the time taken for the most general quantum dynamics. Our methods rely on measuring angles and distances between (mixed) states represented as generalized Bloch vectors. We study the properties of our bound and present its form for closed and open evolution, with the latter in both Lindblad form and in terms of a memory kernel. Our speed limit is provably robust under composition and mixing, features that largely improve the effectiveness of quantum speed limits for open evolution of mixed states. We also demonstrate that our bound is easier to ... READ MORE
- Thales partners with ID Quantique and ISARA to combat the future security threats of quantum computing
**Collaborations with ISARA Corporation and ID Quantique will make quantum-safe crypto more widely available to protect data in the cloud, applications and across networks.**Thales today announced its collaboration with ISARA Corp. and ID Quantique (IDQ), leading providers of complementary quantum-safe security solutions, to collaborate on a quantum-safe, crypto-agile solution designed to protect against the security threat of quantum computing. As the reality of quantum computing approaches, companies and other organizations need to stay one step ahead of the potential computational power that could render today’s encryption algorithms obsolete. By incorporating quantum-safe algorithms from ISARA and the quantum random number generation technology from ID Quantique in its SafeNet Luna Hardware Security Modules (HSM) and SafeNet High Speed Encryptors, Thales is ... READ MORE - Explore your PhD and Master’s options with Physics World Careers 2019With the start of the new academic year fast approaching at many universities around the world, now is the perfect time for final-year physics students to start thinking about what they’ll do after graduation. Many students will naturally have their eyes on a master’s or PhD, hoping to finally do some “proper” research after all those years studying textbooks. It’ll be your chance to perhaps be the next Curie, Hawking or Einstein. But knowing what to do for at post-graduate level can be hard – there are almost too many options out there, from astronomy to Z-bosons. With that in mind, the bumper
*Physics World Careers 2019*guide is here to help, available free-to-read in both print and digital formats. ... READ MORE - Random coding for sharing bosonic quantum secretsAuthor(s): Francesco Arzani, Giulia Ferrini, Frédéric Grosshans, and Damian MarkhamWe consider a protocol for sharing quantum states using continuous variable systems. Specifically we introduce an encoding procedure where bosonic modes in arbitrary secret states are mixed with several ancillary squeezed modes through a passive interferometer. We derive simple conditions on the int...[Phys. Rev. A 100, 022303] Published Mon Aug 05, 2019 ... READ MORE
- Quantum microphone detects the presence of phononsA superconducting qubit can be used to reliably detect the presence of multiple phonons at the same time, US physicists have demonstrated. Patricio Arrangoiz-Arriola and colleagues at Stanford University built their “quantum microphone” using materials that minimized phonon losses, while narrowing the spectra of their qubit’s emissions to reduce uncertainties. The technology could allow for new capabilities in quantum computing, including modems that link together many quantum computers at different locations. While the quantum properties of photons have been explored and exploited extensively, those of quantized mechanical vibrations, known as phonons, have remained much more difficult to study. Although phonons are important for explaining many properties in solid materials, the technologies required to measure and control them have faced significant ... READ MORE
- Method to determine which quantum operations can be realized with linear optics with a constructive implementation recipeAuthor(s): Juan Carlos Garcia-Escartin, Vicent Gimeno, and Julio José Moyano-FernándezThe evolution of quantum light through linear optical devices can be described by the scattering matrix S of the system. For linear optical systems with m possible modes, the evolution of n input photons is given by a unitary matrix U=φm,M(S), derived from a known homomorphism, φm,M, which depends o...[Phys. Rev. A 100, 022301] Published Fri Aug 02, 2019 ... READ MORE
- Portable scanner could boost point-of-care brain MRI©
*AuntMinnie.com*The ability to perform a whole-brain MRI scan at the point-of-care for patients with mobility challenges could soon become a reality with a portable, lightweight device now under development by researchers at the Massachusetts Institute of Technology (MIT). The low-field, helmet-like scanner could overcome large-scale financial investments and structural requirements of siting conventional, long-bore, 1.5- and 3-tesla MRI systems. What’s more, the developers believe the work-in-progress system will ultimately yield diagnostic-quality images and enable healthy outcomes for patients. “This [device] is built on a large body of work, with innovation and a design that is focused on an appropriate size that fits around an adult’s head,” said co-developer Patrick McDaniel, a doctoral student in MIT’s electrical engineering program. “It ... READ MORE - Observation of a symmetry-protected topological phase of interacting bosons with Rydberg atomsThe concept of topological phases is a powerful framework to characterize ground states of quantum many-body systems that goes beyond the paradigm of symmetry breaking. Topological phases can appear in condensed matter systems naturally, whereas the implementation and study of such quantum many-body ground states in artificial matter requires careful engineering. Here, we report the experimental realization of a symmetry-protected topological phase of interacting bosons in a one-dimensional lattice, and demonstrate a robust ground state degeneracy attributed to protected zero-energy edge states. The experimental setup is based on atoms trapped in an array of optical tweezers and excited into Rydberg levels, which gives rise to hard-core bosons with an effective hopping generated by dipolar exchange interaction. ... READ MORE
- Is your Supercomputer Stumped? There May Be a Quantum Solution(Credit: iStock/metamorworks) S
**ome math problems are so complicated**that they can bog down even the world’s most powerful supercomputers. But a wild new frontier in computing that applies the rules of the quantum realm offers a different approach. A new study led by a physicist at Lawrence Berkeley National Laboratory (Berkeley Lab), published in the journal Scientific Reports, details how a quantum computing technique called “quantum annealing” can be used to solve problems relevant to fundamental questions in nuclear physics about the subatomic building blocks of all matter. It could also help answer other vexing questions in science and industry, too.**Seeking a quantum solution to really big problems**“No quantum annealing algorithm exists for ... READ MORE - Nanotechnology for quantum computers, industry skills for physics students, technologies that make physics happenThis week’s podcast features an interview with Ray LaPierre, who heads up the department of engineering physics at McMaster University in Canada. Ray talks to fellow Canadian Hamish Johnston about his research in semiconductor nanowires, in particular for use in photonics and quantum computers, and also shares his experiences of working at JDS Uniphase during the telecoms boom.
*Physics World*‘s Anna Demming also joins the podcast to describe a flurry of new results in the emerging field of twistronics – where two layers of graphene are stacked on top of each other but twisted at a slight angle to each other. The discovery last year that bilayer graphene can become a superconductor if the two graphene layers are twisted at ... READ MORE - Advanced Photon Source set for $815m upgradeThe US Department of Energy (DOE) has given the green light to a major upgrade of Argonne National Laboratory’s Advanced Photon Source. Costing $815m, the upgrade will see the “brightness” of the synchrotron boosted by up to three orders of magnitude allowing researchers to study materials and processes at an unprecedented level. There are around 50 synchrotron light sources in 23 different countries around the world. These machines work by accelerating electrons to high energies and then injecting them into a circular storage ring where they emit powerful beams of X-rays. The X-rays act as a microscope and can be used to study the structure and properties of materials in a range of disciplines, from condensed-matter physics to biology. The APS has ... READ MORE
- Synopsis: Spectral Evidence of a Supersolid Made of Cold AtomsResearchers find new evidence that a Bose-Einstein condensate made of erbium atoms undergoes a phase transition into a bizarre form of quantum matter.[Physics] Published Thu Aug 01, 2019 ... READ MORE
- Additive manufacturing makes vacuum systems smaller, lighter and smarterIf quantum technologies came with instruction manuals, the first few pages would describe how to cool and trap a sample of atoms. Clouds of cold, trapped atoms lie at the heart of present-day quantum devices such as atomic clocks. They’re also integral to several possible future ones, such as the “quantum positioning systems” that may one day replace satellite-based GPS. The reason is simple: it is only by isolating atoms from their environment and cooling them down, sometimes to temperatures as low as a fraction of a degree above absolute zero, that their quantum characteristics come to the fore. Properties such as the atoms’ acceleration and rotation, the timing and frequency of transitions between energy levels, and even their response ... READ MORE