Generation of a Superposition of Odd Photon Number States for Quantum Information Networks

TLDR

In the low‑squeezing limit, the generated state reduces to a single‑photon state. The state is produced by photon subtraction from a continuous‑wave squeezed vacuum generated by an optical parametric amplifier, yielding ~10,000 events per second in a near‑perfect spatial mode with a Fourier‑limited bandwidth compatible with atomic quantum memories. Experimentally, the authors observed quantum‑network‑compatible light with a nonpositive Wigner function that ideally forms a coherent superposition of odd photon number states, making it an excellent input for testing quantum memories, repeaters, and linear‑optics quantum computers.

Abstract

We report on the experimental observation of quantum-network-compatible light described by a nonpositive Wigner function. The state is generated by photon subtraction from a squeezed vacuum state produced by a continuous wave optical parametric amplifier. Ideally, the state is a coherent superposition of odd photon number states, closely resembling a superposition of weak coherent states |alpha > - |-alpha >. In the limit of low squeezing the state is basically a single photon state. Light is generated with about 10,000 and more events per second in a nearly perfect spatial mode with a Fourier-limited frequency bandwidth which matches well atomic quantum memory requirements. The generated state of light is an excellent input state for testing quantum memories, quantum repeaters, and linear optics quantum computers.