Verified Quantum Information Scrambling

Synopsis

Although the resources needed to achieve the speedups anticipated by many quantum algorithms are still out of reach, near-term quantum computers are capable of addressing some genuine physics problems. I will be discussing a demonstration of verified quantum information scrambling using an ion trap quantum computer. Quantum scrambling is a process in which local information is spread over many-body quantum entanglements and correlations. However, experimental measurement of quantum scrambling is challenging due to the complexity of the many-body entangled states. The authors of the paper I will review implement a quantum circuit to test for scrambling through conditional teleportation of a quantum state. This provides an unambiguous test for scrambling while also characterizing the degree of quantum chaos by measuring the out-of-time correlation function. They implement and test a scrambling process using a tunable three-qubit unitary operation on a seven-qubit circuit using an ion trap quantum computer. I will discuss their implementation, the results of their tests, and the prospects for future measurements utilizing near-term quantum computers.

K. A. Landsman et al., Nature 567, 2019. https://doi.org/10.1038/s41586-019-0952-6