Solving Coherence and Initialization Problems of Qubits with Hybrid Qubits. Researchers at Japan’s RIKEN Center for Emergent Matter Science have succeeded in creating a device – an architecture based on semiconductors – for quantum computing which solves two problems plaguing the furtherance of quantum computing. Speed is critical to developing quantum computers, “First, the device must be able to be initialized quickly. Initialization is the process of putting a qubit into a certain state, and if that cannot be done rapidly it slows down the device. Second, it must maintain coherence for a time long enough to make a measurement. Coherence refers to the entanglement between two quantum states.” A long-enough coherence of the entangled qubits is needed to make a measurement – a “read out.” The result of a quantum calculation depends on the coherent state.
The hybrid qubits are composed of a single-spin qubit called a Loss-DiVincenzo qubit; its coherence time is ample for read-outs. “The second type, called a singlet-triplet qubit, is quickly initialized and read out, but it quickly becomes decoherent.” Combining the two, types of qubits were combined within the device architecture (known as a controlled-phase gate).
This combination within the architecture developed by the RIEKN team “allowed spin states to be entangled between the qubits in a time fast enough to maintain the coherence, allowing the state of the single-spin qubit to be read out by the fast singlet-triplet qubit measurement.”
Further study will determine if the qubit hybridization coupled with the controlled-phase gate architecture will lend to quantum computer scalability.
“Spin-based quantum computers have the potential to tackle difficult mathematical problems that cannot be solved using ordinary computers, but many problems remain in making these machines scalable. Now, an international group of researchers led by the RIKEN Center for Emergent Matter Science have crafted a new architecture for quantum computing. By constructing a hybrid device made from two different types of qubit—the fundamental computing element of quantum computers—they have created a device that can be quickly initialized and read out, and that simultaneously maintains high control fidelity. Schematic of the device [above].” (Image cradit: RIKEN Center for Emergent Matter Science, Japan)