Schrödinger cat states in continuous variable non-Gaussian networks

I. V. Sokolov

We propose a non-Gaussian continuous variable (CV) gate which is able to conditionally produce superposition of two "copies" of an arbitrary input state well separated in the coordinate and momentum plane - a Schrödinger cate state. The gate uses cubic phase state of an ancillary oscillator as a non-Gaussian resource, an entangling Gaussian gate, and homodyne measurement which provides nonunique information about the target system canonical variables, which is a key feature of the scheme. We show that this nonuniqueness manifests problems which may arise by extension of the Heisenberg picture onto the measurement-induced evolution of CV non-Gaussian networks, if this is done in an approach commonly used for CV Gaussian schemes of quantum information.

Marek Sawerwain, Roman Gielerak

Ananga Mohan Datta, William J. Munro, Nicolo Lo Piparo +1 more

Entangled coherent states (ECS) provide a powerful non-Gaussian resource for continuous-variable quantum communication, but their generation in scalable architectures remains challenging. We propose an integrated photonic scheme that creates high-fidelity ECS from a two-mode squeezed vacuum via photon subtraction in a symmetric waveguide trimer. The resulting non-Gaussian entanglement is further enhanced by single-photon catalysis, which purifies the distributed state after transmission through lossy channels. Using these purified ECS resources, we analyze a photon-number-based teleportation protocol and demonstrate high-fidelity transfer of both coherent states and Schrodinger cat states. In particular, the teleportation fidelity for cat states exceeds the classical threshold of 2/3 over a broad range of realistic channel and squeezing parameters, whereas Gaussian resources fail to do so. Our results show that integrated photon subtraction and catalysis enable practical, chip-compatible generation of non-Gaussian entanglement suitable for advanced quantum teleportation and continuous-variable quantum networks.

K. Kong Wan, David Menzies

Michael W. Noel, Carlos R. Stroud

Kaushik Parasuram Seshadreesan, Jonathan P Dowling, G. S. Agarwal

In continuous-variable quantum information, non-Gaussian entangled states that are obtained from Gaussian entangled states via photon subtraction are known to contain more entanglement. This makes them better resources for quantum information processing protocols, such as, quantum teleportation. We discuss the teleportation of non-Gaussian, non-classical Schrödinger-cat states of light using two-mode squeezed vacuum light that is made non-Gaussian via subtraction of a photon from each of the two modes. We consider the experimentally realizable cat states produced by subtracting a photon from the single-mode squeezed vacuum state. We discuss two figures of merit for the teleportation process, (a) the fidelity, and (b) the maximum negativity of the Wigner function at the output. We elucidate how the non-Gaussian entangled resource lowers the requirements on the amount of squeezing necessary to achieve any given fidelity of teleportation, or to achieve negative values of the Wigner function at the output.