Generation of Large Number-Path Entanglement Using Linear Optics and Feed-Forward

Abstract

We show how an idealised measurement procedure can condense photons from two modes into one, and how, by feeding forward the results of the measurement, it is possible to generate efficiently superpositions of components for which only one mode is populated, commonly called ``N00N states''. For the basic procedure, sources of number states leak onto a beam splitter, and the output ports are monitored by photodetectors. We find that detecting a fixed fraction of the input at one output port suffices to direct the remainder to the same port with high probability, however large the initial state. When instead photons are detected at both ports, Schrödinger cat states are produced. We describe a circuit for making the components of such a state orthogonal, and another for subsequent conversion to a N00N state. Our approach scales exponentially better than existing proposals. Important applications include quantum imaging and metrology.

References in corpus (6)

• Reference frames, superselection rules, and quantum information
• Beating the Standard Quantum Limit with Four Entangled Photons
• Generalized Limits for Single-Parameter Quantum Estimation
• High-speed linear optics quantum computing using active feed-forward
• Photon-number superselection and the entangled coherent-state representation
• Conditional generation of path-entangled optical NOON states

Cited by in corpus (4)

• Quantum Optical Metrology -- The Lowdown on High-N00N States
• Preparation of entangled states of two photons in several spatial modes
• Amplification of polarization NOON states
• Quantum enhancement of N-photon phase sensitivity by interferometric addition of down-converted photon pairs to weak coherent light