Tomography of mode-tunable coherent single-photon subtractor
Young-Sik Ra, Clément Jacquard, Adrien Dufour, Claude Fabre, Nicolas Treps · 2017
Summary form only given. Single-photon subtracting operation plays important roles in photonic quantum information processing. For example, it enables distillation of entanglement, noiseless amplification of a quantum state, and enhancement of measurement precision. In particular, the non-Gaussian characteristic of the operation is essential for genuine speed-up and universality of continuous-variable quantum computing. Until now, implementation of single-photon subtraction has been limited on a single-mode or a two-mode quantum state, but recently, extension to multiple modes attracts attention [1, 2] in accordance with the availability of multimode quantum states [3].In this work, we implement a mode-tunable coherent single-photon subtractor which can be tuned to subtract a single photon exclusively from one time-frequency mode or coherently from multiple time-frequency modes. To characterize the single-photon subtractor, we introduce a matrix representation (called a subtraction matrix) of a general single-photon subtractor and measure the matrix by employing coherent-state quantum process tomography [5]. We found that characterizing a single-photon subtractor can be significantly simplified compared with the original coherent-state quantum process tomography because the success probability of a single-photon subtractor alone provides complete information of the device.