Adding Noise to Preserve Quantum Process Fidelity
Abstract
Noise from environmental degrees of freedom can severely limit the fidelity of quantum information processes. In this project, a procedure for mitigating the harmful effects of environmental noise will be experimentally tested. This procedure relies on the deliberate addition of more noise which is specially designed to counteract the environmental noise. It is theoretically predicted that this ÒcorrectiveÓ noise will allow for quantum process fidelity to be partially recovered. In this project, one specific form of environmental noise will be testedÑ Markovian (i.e. white) noise affecting the phase of a qubit superposition. For this case, theory predicts that adding telegraph noise with a Poisson-distributed autocorrelationÑtermed Ògeneralized MarkovianÓ noiseÑwill cause the coherence of the superposition to oscillate as well as decay, periodically recovering above the coherence that would be present under the influence of only the environmental noise. This prediction will be tested experimentally using a superconducting transmon qubit, with the goal of answering the questions: ¥ Can process fidelity be recovered by adding noise? ¥ What are the experimental limitations on implementing the theoretical proposal? ¥ What should future experimental and theoretical work focus on to better implement noise mitigation? In the proposed tests, the ÒenvironmentalÓ noise will be deliberately added so that it may be fully controlled and characterized. This noise will take the form of white noise in the qubit transition frequency, implemented either by coupling a noisy flux tone into a transmon SQUID loop or by coupling a noisy microwave tone to induce an AC Stark shift. The additional generalized Markovian noise will be added in the same way. A Hahn echo sequence will be used to test the dephasing time; the hypothesis is that the typical exponential decay of coherence will be replaced by a decaying oscillation which periodically rises above the typical exponential curve. The dependence of this behavior on the strength and spectral character of the generalized Markovian will be measured, and the limits on the procedureÕs effectiveness will be tested. The project is expected to take 9 months (beginning in February 2019) and to cost $60k; the vast majority of the cost will be personnel expenses, with a small (~$5k) amount going to cover device fabrication costs.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Feb 14, 2019
- Source ID
- W911NF1910070
Entities
People
- Eli Levenson-Falk
Organizations
- Army Contracting Command
- United States Army
- University of Southern California