Efficient Learning of Continuous-Variable Quantum States

Understand

The characterization of continuous-variable quantum states is crucial for applications in quantum communication, sensing, simulation and computing.

• However, a full characterization of multimode quantum states requires a number of experiments that grows exponentially with the number of modes.
• Here we propose an alternative approach where the goal is not to reconstruct the full quantum state, but rather to estimate its characteristic function at a given set of points.
• For multimode states with reflection symmetry, we show that the characteristic function at M points can be estimated using only O(log M ) copies of the state, independently of the number of modes.