Efficient Z gates for quantum computing

By David C. McKay, Christopher J. Wood, S. Sheldon, Jerry M. Chow, Jay M. Gambetta. 2016

582 citations recorded by the source corpus.

For superconducting qubits, microwave pulses drive rotations around the Bloch sphere. The phase of these drives can be used to generate zero-duration arbitrary virtual $Z$ gates, which, combined with two ${X}_{\ensuremath{\pi}/2}$ gates, can generate any SU(2) gate. Here we show how to best utilize these virtual $Z$ gates to both improve algorithms and correct pulse errors. We perform randomized benchmarking using a Clifford set of Hadamard and $Z$ gates and show that the error per Clifford is reduced versus a set consisting of standard finite-duration $X$ and $Y$ gates. $Z$ gates can correct unitary rotation errors for weakly anharmonic qubits as an alternative to pulse-shaping techniques such as derivative removal by adiabatic gate (DRAG). We investigate leakage and show that a combination of DRAG pulse shaping to minimize leakage and $Z$ gates to correct rotation errors realizes a 13.3 ns ${X}_{\ensuremath{\pi}/2}$ gate characterized by low error $[1.95(3)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}]$ and low leakage $[3.1(6)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}]$. Ultimately leakage is limited by the finite temperature of the qubit, but this limit is two orders of magnitude smaller than pulse errors due to decoherence.

Subfields: Artificial Intelligence, Atomic and Molecular Physics, and Optics

View Paper: https://www.semanticscholar.org/paper/c650050b648c05c54651399505b18048e1f48fc8

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In Atomic and Molecular Physics, and Optics

Citations in the corpus

Dynamical decoupling for superconducting qubits: A performance survey (2022, background): “The reason is that Y is compiled into Z v − X where Z v denotes a virtual Z gate [94].”
Simulation of quantum circuits by low-rank stabilizer decompositions (2018, background): “From the experimental perspective, single-qubit Z-rotations are often the most reliable elementary operations [43].”
High-Fidelity, Frequency-Flexible Two-Qubit Fluxonium Gates with a Transmon Coupler (2023, background): “These single-qubit phase corrections can be conveniently implemented through virtual-Z gates by adjusting the phases of subsequent single-qubit gates [39].”
Software Mitigation of Crosstalk on Noisy Intermediate-Scale Quantum Computers (2020, methodology): “For example, in IBMQ systems, gates are implemented by driving the qubits with microwave voltage pulses [40].”
High fidelity two-qubit gates on fluxoniums using a tunable coupler (2022, background): “We experimentally demonstrate fSim-type and controlled-Z-gates with 99.55 and 99.23% fidelities, respectively.”