Optical Einstein-Podolsky-Rosen Correlations

Virendra Singh

Wenqiang Qin, jiale li, Yonglin Bai +3 more

Einstein-Podolsky-Rosen (EPR) steering, a distinct class of quantum correlation intermediate between entanglement and Bell nonlocality, exhibits unique asymmetry and directionality. EPR steering swapping, analogous to entanglement swapping, enables two initially independent particles to establish EPR steering correlations. Recent advances in all-optical entanglement and EPR steering swapping have overcome the limitation of mutual electro-optical conversions. However, for quantum information systems required in real-world applications, extending these capabilities to multimode regimes remains largely underexplored. Here, we propose an m -to- n multimode all-optical EPR steering swapping architecture based on energy-level-cascaded four-wave mixing processes. By harnessing fundamental light-atom interactions, we demonstrate scalable multimode EPR steering swapping and realize non-Hermitian control over dressing-induced coherent channels. Crucially, our multimode approach demonstrates distinctive, mode-dependent features of non-monotonicity and asymmetry, which are unattainable in conventional two-mode schemes. The flexible controllability afforded by such multimode quantum correlations also facilitates interfaces between non-Hermitian light-matter systems, paving the way for practical implementations of EPR steering and all-optical quantum networks.

K. W�dkiewicz

Russell Bloomer, Matthew Pysher, Olivier Pfister

We present the experimental realization of a theoretical effect discovered by Olivares and Paris (2009 Phys. Rev. A 80 032329), in which a pair of entangled optical beams undergoing independent losses can see nonlocal correlations restored by the use of a nonlocal resource correlating the losses. Twin optical beams created in an entangled, Einstein–Podolsky–Rosen (EPR) state by an optical parametric oscillator above threshold were subjected to 50% loss from beamsplitters in their paths. The resulting severe degradation of the amplitude-quadrature correlations between the two beams was then suppressed when another, independent EPR state impinged upon the other input ports of the beamsplitters, effectively entangling the losses inflicted to the initial EPR state. The additional EPR beam pair was classically coherent with the primary one but had no quantum correlations with it. This result may find applications as a 'quantum tap' for entanglement.

Marlan O. Scully, Yakir Aharonov, Berthold‐Georg Englert

Adam Bennet

Shared quantum correlations find application in a wide range of modern quantum information protocols. This thesis presents several optical experiments towards the improved certification of shared quantum correlations, using photonic qubits. The first experiment demonstrates the Einstein–Podolsky–Rosen (EPR) steering effect with no detection loophole. Polarisation–entangled photon pairs generated in a Sagnac interferometer were used to test new loss–tolerant EPR steering inequalities. To test the robustness of the loss–tolerant EPR steering nequalities, a transmission loss of −4.3dB was introduced using a 1km optical fibre loop, finding inequality violations for n = 10 and n = 16 measurement settings with no detection loophole (equating to a total loss of 87%). The findings demonstrate how the new loss–tolerant protocols can be used to certify the EPR steering effect for arbitrarily high losses, and may find application in one–sided device–independent quantum key distribution protocols. The second experiment introduces EPR steering in the context of an EPR steering game. The rules of the game allow for certification of shared quantum correlations via EPR steering inequalites without requiring trust in devices or parties external to a quantum referee. In particular, the experiment successfully demonstrates EPR steering in a measurement–device independent framework; a framework which has typically been accessible only through Bell inequality violations. The findings suggest the possibility for quantum–refereed one–sided device–independent quantum key distribution protocols.