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arXiv:quant-ph/0011081 · Physical Review Letters

Multiparticle Quantum Superposition and Stimulated Entanglement by Parity Selective Amplification of Entangled States

F. De Martini, Giovanni Di Giuseppe, Sebastião Pádua

Published Sep 25, 2001• 28 citations
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Abstract

We report the creation of an entangled multiphoton quantum superposition by quantum injection of entangled 2-photon states into a parity selective parametric amplifier. The information preserving property of the state transformation suggests for these macrostates the name of large qubits. They are ideal objects for investigating the emergence of the classical world in complex quantum systems and have relevant new applications in quantum information.

DOI
10.1103/physrevlett.87.150401

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The present work investigates quantum phenomena with large size systems generated in the microscopic world and then transferred in the macro one through an amplification process. Precisely, a microscopic entangled photon state is created by a nonlinear optical process, then one subsystem is injected into an optical parametric amplifier and then converted into a macro — state consisting of N ≈ 3.5 × 104 photons in a quantum superposition. By adopting a local filtering technique, we then demonstrate the entanglement of the bipartite system. The new conceptual framework paves the way toward the generation of light-matter entangled states by coupling the output radiation with a Bose-Einstein condensate. The multiphoton superposition generated by a quantum-injected optical parametric amplifier (QI-OPA) can be made to interact with a Mirror-BEC shaped as a Bragg interference structure.
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The new process of quantum injection into an optical parametric amplifier operating in entangled configuration is adopted to ``amplify'' into a large dimensionality spin- 12\frac{1}{2}21​ Hilbert space the quantum entanglement and superposition properties of the photon couples generated by parametric down-conversion. The structure of the Wigner function and of the field's correlation functions shows a decoherence-free multiphoton Schroedinger-cat behavior of the emitted field which is largely detectable against the squeezed-vacuum noise.
In the present work we propose to realize a macroscopic light-matter entangled state, obtained by the interaction of a multiphoton quantum superposition with a BEC system. The multiphoton quantum state is generated by a quantum-injected optical parametric amplifier (QI-OPA) seeded by a single-photon belonging to an EPR entangled pair and interacts with a Mirror-BEC shaped as a Bragg interference structure. The overall process will realize an entangled macroscopic quantum superposition involving a "microscopic" single-photon state of polarization and the coherent "macroscopic" displacement of the BEC structure acting in space-like separated distant places. This hybrid photonic-atomic system could open new perspectives on the possibility of coupling the amplified radiation with an atomic ensemble, a Bose-Einstein condensate, in order to implement innovative quantum interface between light and matter.