Using Diamond Qubits, Researchers Maintain Quantum State Coherence for > 60 Seconds

Diamond-Based Qubits Set New Coherence Record

In brief…

+  Researchers have created a diamond-based quantum memory device that can retain a quantum state for more than a minute, making it the most stable quantum memory device of its kind… The new device relies on a flaw in the diamond called a nitrogen vacancy site, where two carbon atoms in the diamond are replaced by a nitrogen atom and an empty site.

The potential for diamonds to be used in quantum computers has prompted scientists to try to grow the perfectly flawed diamond, building it atom by atom with holes and defects located exactly where they should be, instead of leaving it up to nature and chance.

+  While using flawed crystals for storing quantum information is not a new concept, the 10-qubit system is the largest qubit-register of its kind. The researchers were also able to generate entanglement between all 45 possible qubit pairs among the 10 qubits, an achievement relevant to many quantum network applications.

+  The quantum memory can retain a single qubit state for over 75 seconds, a task akin to holding the state in memory. It can also maintain a two-qubit entanglement for over 10 seconds, which is necessary for the device to function like a processor and perform certain calculations. The researchers published the results in a recent paper in the journal Physical Review X.

+  While a long coherence time is important, it is not the only objective that researchers must strive for when designing quantum systems. “Comparing different systems is usually a bit tricky and can upset people because there are other things that matter,” said Bradley. “There are other systems that are very good at what they do.”

+  For example, quantum systems that use superconducting circuitries, which companies such as Google and IBM are developing, are generally more configurable — since they are not literally set in stone like diamond memories are. But they are usually bulkier and have shorter coherence times. The ability for diamond qubits to interact with light also makes them more suitable for certain applications such as long-range quantum communications, which are mostly done using lasers.

Source:  INSIDE SCIENCE.  Yuen Yiu,  Diamond-Based Qubits Set New Coherence Record…

Content may have been edited for style and clarity.