Farzam Nosrati - University of Ottawa

Photonic DQC1 with Structured Light for Quantum Sensing Applications

Deterministic quantum computation with one qubit (DQC1) is a fundamental model of quantum information processing in which a single partially pure qubit, together with a highly mixed n-qubit register, is used. The DQC1 circuit model allows for the estimation of the normalized trace of a unitary matrix. In parallel, photonic quantum circuits based on structured light provide access to high-dimensional Hilbert spaces, offering a versatile platform for both fundamental studies and emerging quantum technologies. Here, we combine these ideas and introduce a modified version of DQC1 for quantum sensing using spatial-qudit encoding. We show that this modified DQC1 circuit repurposes matrix trace estimation as a sensing method, enabling applications ranging from quantum phase estimation to quantum hypothesis testing. We experimentally implement the protocol using a photonic circuit based on spatially structured light. Our platform performs quantum phase estimation and can be used to estimate properties of a medium, such as scattering and turbulence strength. We further reformulate the DQC1 circuit as a quantum hypothesis testing protocol for a quantum illumination-based application. Our findings indicate that spatially structured qudit-based photonic DQC1 can function as a platform for quantum sensing, even with minimal single-qubit purity and highly mixed states.