July 6, 2023 report
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Millisecond coherence reached for fluxonium qubit
A team of physicists at the University of Maryland's Joint Quantum Institute and Quantum Materials Center has achieved millisecond coherence while testing the properties of a fluxonium qubit in a quantum circuit. In their study, reported in the journal Physical Review Letters, the group made some small changes to the circuit parameters controlling the qubit to increase relaxation times.
As physicists and engineers around the world pursue the goal of building a truly useful quantum computer, some researchers are investigating the amount of time that a qubit can maintain its quantum properties—currently, it is too short, which tends to result in entanglement issues. To that end, research teams have been focusing on the properties of superconducting qubits, such as transmons, which are the type currently used by IBM and Google in their research efforts.
In this new study, the researchers focused their attention on a different superconducting qubit called a fluxonium. Prior research had suggested it may not be suitable for quantum circuit applications due to the short availability time of its quantum properties. But the team has found a way to increase that time by a factor of 10 over previous efforts.
In their work, the research team took a closer look at the relaxation time of the fluxonium—the time during which the qubit moves between states and the time during which the data it stores can be used. They found that if they reduced the operating frequency by optimizing circuit parameters, they could increase the availability (coherence) time of the qubit, bringing its time nearly up to that of transmons, marking them as a possible alternative. More specifically, they found they could increase the coherence time to over 1.43 milliseconds—10 times longer than anyone else has managed to achieve.
The research team also found evidence suggesting that more tweaking could lead to even longer coherence times, possibly making fluxonium a better choice for use in future quantum circuit research efforts.
More information: Aaron Somoroff et al, Millisecond Coherence in a Superconducting Qubit, Physical Review Letters (2023). DOI: 10.1103/PhysRevLett.130.267001. On arXiv: DOI: 10.48550/arxiv.2103.08578
Journal information: Physical Review Letters , arXiv
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