Multiplexing-enhanced Advanced Quantum State Engineering

Photons are excellent carriers of quantum information and will certainly play a critical role in quantum technologies spanning communication, computing, and metrology. Such quantum technologies will play (and are playing) an important role in advancing science as well as the national health, prosperity and welfare, along with securing the national defense. Producing efficient sources of pure single- and multi-photon states is a key step towards the broad deployment of such quantum technologies. However, creating these quantum states of light efficiently remains a challenge, preventing their widespread use. This project seeks to combine established photon sources with low-loss optical buffers and switches to efficiently generate these complex forms of light. To confirm that our sources indeed generate the desired quantum states, we will also develop advanced techniques to characterize the produced light. Lastly, we will demonstrate how our efficient and well-characterized sources of single and multi-photon states can enable new advances in communication, computing, and metrology. We leverage repeated “photon-addition” operations with nonlinear-optics sources of heralded photons to efficiently create multi-photon states of light such as Fock states, heralded bipartite entangled states, and “N00N” and related states. Similar multiplexing methods also allow near-deterministic photon subtraction, which enables another entire class of states to be generated by starting with coherent or squeezed states. Combined, these techniques allow the bottom-up engineering of a wide variety of exotic quantum states that are otherwise nearly impossible to generate. To assess the quantum mechanical nature of these states, well-established techniques for basic single-photon states need to be extended to and validated for multi-photon states. Examples include multi-photon interference, photon autocorrelation measurements, and homodyne detection. Lastly, we will illustrate the value of these multi-photon states via several demonstrations, including calibrating photon-number-resolving detectors with Fock states and validating phase sensitivity beyond the classical shot-noise limit with N00N states. Long-term impacts of this work include facilitating new technologies such as quantum error correction codes based on N00N and related states (potentially useful for future quantum networking applications), quantum simulations with Fock states, and practical quantum metrology beyond the classical shot-noise limit. Additionally, a hybrid continuous-variable-discrete-variable (CVDV) state-characterization system based on homodyne detection could enable the exploration of CV-encoded quantum states (e.g., squeezed states or cluster states) as well as hybrid CVDV states (e.g., cat states), with applications in measurement-based quantum computation. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.