Abstract
Accurate control of two-level systems is a longstanding problem in quantum mechanics. One such quantum system is the frequency-bin qubit: A single photon existing in superposition of two discrete frequency modes. In this Letter, we demonstrate fully arbitrary control of frequency-bin qubits in a quantum frequency processor for the first time. We numerically establish optimal settings for multiple configurations of electro-optic phase modulators and pulse shapers, experimentally confirming near-unity mode-transformation fidelity for all fundamental rotations. Performance at the single-photon level is validated through the rotation of a single frequency-bin qubit to 41 points spread over the entire Bloch sphere, as well as tracking of the state path followed by the output of a tunable frequency beam splitter, with Bayesian tomography confirming state fidelities Fρ>0.98 for all cases. Such high-fidelity transformations expand the practical potential of frequency encoding in quantum communications, offering exceptional precision and low noise in general qubit manipulation.
| Original language | English |
|---|---|
| Article number | 120503 |
| Journal | Physical Review Letters |
| Volume | 125 |
| Issue number | 12 |
| DOIs | |
| State | Published - Sep 2020 |
| Externally published | Yes |
Funding
This research was performed in part at Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the U.S. Department of Energy under Contract No. DE-AC05-00OR22725. Funding was provided by the U.S. Department of Energy, Office of Science (Office of Advanced Scientific Computing Research, Early Career Research Program; and Office of Workforce Development for Teachers and Scientists Science Undergraduate Laboratory Internship Program) and the National Science Foundation (Grant No. 1839191-ECCS).