Demonstration of quantum volume 64 on a superconducting quantum computing system

Abstract

We improve the quality of quantum circuits on superconducting quantum computing systems, as measured by the quantum volume, with a combination of dynamical decoupling, compiler optimizations, shorter two-qubit gates, and excited state promoted readout. This result shows that the path to larger quantum volume systems requires the simultaneous increase of coherence, control gate fidelities, measurement fidelities, and smarter software which takes into account hardware details, thereby demonstrating the need to continue to co-design the software and hardware stack for the foreseeable future.

Quality, Speed, and Scale: three key attributes to measure the performance of near-term quantum computers

“…Random unitaries capture average circuits and how they may explore the Hilbert space. These may be compiled using a variety of methods to the target gate set [4]. The quality of the circuits will be dictated to a great extent by how well this compiler performs.…”

“…Quantum volume is sensitive to coherence, gate fidelity, and measurement fidelity which are hardware properties of a quantum processor. Quantum volume is also influenced by connectivity and compilers which can make circuits efficient to minimize the effect of decoherence [4]. Quantum volume is a holistic metric because it cannot be improved by just improving one aspect of the system, but rather requires all parts of the system to be improved in a synergistic manner.…”

Variational quantum algorithm with information sharing

“…Rapid developments in quantum computing hardware [1][2][3] have led to an explosion of interest in nearterm applications [4][5][6][7][8]. Though current devices are remarkable feats of engineering, their current coherence times and gate fidelities exclude running general quantum algorithms such as Shor's factorisation, Grover search or quantum phase estimation.…”

Quantum crosstalk cancellation for fast entangling gates and improved multi-qubit performance

“…where ∆ 0,1 represents the qubit-qubit detuning. This crosstalk has been seen to be an important limitation to multi-qubit circuit performance in tests of quantum volume [3], randomized benchmarking [4], and error correction codes [5], and may prevent device scaling [6]. Several hardware strategies have been employed to mitigate this crosstalk.…”