Authors: Frank Arute, Kunal Arya, Ryan Babbush, Dave Bacon, Joseph C. Bardin, Rami Barends, et al. (Google AI Quantum & UC Santa Barbara)
Demonstrated sampling of pseudo-random quantum circuits on a 53-qubit 2D transmon array with tunable couplers, verified via Linear Cross-Entropy Benchmarking (XEB) in 200 seconds.
Key Quantitative & Theoretical Takeaway: Linear XEB fidelity F_XEB correlates the measured bitstring probabilities with ideal Porter-Thomas amplitudes, enabling verification of full-circuit fidelity from sub-circuit benchmarks.
The promise of quantum computers is that certain computational tasks might be executed exponentially faster on a quantum processor than on a classical processor. Here we report the use of a processor with programmable superconducting qubits to create quantum states on 53 qubits.
Linear XEB is defined as F_XEB = (2^n * mean(P(x_i))) - 1, where P(x_i) is the ideal theoretical probability of bitstring x_i sampled by the quantum processor. An ideal Porter-Thomas distribution yields F_XEB = 1 while uniform decoherence yields F_XEB = 0.
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