A macroscopic quantum state analysed particle by particle

Abstract

Explaining how microscopic entities collectively produce macroscopic phenomena is a fundamental goal of many-body physics. Theory predicts that large-scale entanglement is responsible for exotic macroscopic phenomena, but observation of entangled particles in naturally occurring systems is extremely challenging. Synthetic quantum systems made of atoms in optical lattices have been con- structed with the goal of observing macroscopic quantum phenomena with single-atom resolution. Serious challenges remain in producing and detecting long-range quantum correlations in these systems, however. Here we exploit the strengths of photonic technology, including high coherence and efficient single-particle detection, to study the predicted large-scale entanglement underlying the macroscopic quantum phenomenon of polarization squeezing. We generate a polarization-squeezed beam, extract photon pairs at random, and make a tomographic reconstruction of their joint quantum state. We present experimental evidence showing that all photons arriving within the squeezing coherence time are entangled, that entanglement monogamy dilutes entanglement with increasing photon density and that, counterintuitively, increased squeezing can reduce bipartite entanglement. The results provide direct evidence for entanglement of macroscopic numbers of particles and introduce micro-analysis to the study of macroscopic quantum phenomena.

References in corpus (23)

• Quantum Simulation
• Entanglement detection
• On the Measurement of Qubits
• A quantum gas microscope - detecting single atoms in a Hubbard regime optical lattice
• Single-Atom Resolved Fluorescence Imaging of an Atomic Mott Insulator
• 14-qubit entanglement: creation and coherence
• Many-particle entanglement with Bose--Einstein condensates
• Nonlinear atom interferometer surpasses classical precision limit
• Bose-Einstein condensation of photons in an optical microcavity
• Entanglement and Extreme Spin Squeezing
• Observation of eight-photon entanglement
• Macroscopic quantum self-trapping and Josephson oscillations of exciton-polaritons
• Single-particle-sensitive imaging of freely propagating ultracold atoms
• Observation of grand-canonical number statistics in a photon Bose-Einstein condensate
• Spin squeezing inequalities for arbitrary spin
• Ultra-Narrow Faraday Rotation Filter at the Rb D1 Line
• Generation of macroscopic singlet states in a cold atomic ensemble
• Low-frequency vacuum squeezing via polarization self-rotation in Rb vapor
• State Tomography: Hidden Differences
• Rubidium resonant squeezed light from a diode-pumped optical-parametric oscillator
• Atomic filtering for hybrid continuous-variable/discrete-variable quantum optics
• Bose-Einstein Condensation of Photons in a Microscopic Optical Resonator: Towards Photonic Lattices and Coupled Cavities
• Optical spin squeezing: bright beams as high-flux entangled photon sources

Cited by in corpus (8)

• Generation of time-frequency grid state with integrated biphoton frequency combs
• Experimental certification of millions of genuinely entangled atoms in a solid
• Entanglement-enhanced phase estimation without prior phase information
• Multi-second magnetic coherence in a single domain spinor Bose-Einstein condensate
• Quantum-Limited Squeezed Light Detection with a Camera
• Light-matter micro-macro entanglement
• Quantum-enhanced phase estimation using optical spin squeezing
• Estimation of covariance matrix of macroscopic quantum states