Phys.org May 9, 2024
Researchers in Japan used a random search technique to find quantum gate sequences that implement perfect quantum state preparation or unitary operator synthesis with arbitrary targets. The approach was based on the recent discovery that there is a large multiplicity of quantum circuits that achieved unit fidelity in performing a given target operation, even at the minimum number of single-qubit and two-qubit gates needed to achieve unit fidelity. They showed that the fraction of perfect-fidelity quantum circuits increased rapidly as soon as the circuit size exceeded the minimum circuit size required for achieving unit fidelity. This result implied that near-optimal quantum circuits for a variety of quantum information processing tasks could be identified relatively easily by trying only a few randomly chosen quantum circuits and optimizing their parameters. They also considered the possibility of using alternative two-qubit gates. And analyzed the case where the two-qubit gate was the B gate, which was known to reduce the minimum quantum circuit size for two-qubit operations. They applied the random search method to the problem of decomposing the four-qubit Toffoli gate and found a 15-cnot-gate decomposition… read more. TECHNICAL ARTICLE
Maximum achievable fidelity F as a function of the number of B gates for unitary operator synthesis… Credit: Phys. Rev. A 109, 052605, 6 May 2024