Two-colour high-purity Einstein-Podolsky-Rosen photonic state

Abstract

We report a high-purity Einstein-Podolsky-Rosen (EPR) state between light modes with the wavelengths separated by more than 200 nm. We demonstrate highly efficient EPR-steering between the modes with the product of conditional variances $${{{{{{{{\mathcal{E}}}}}}}}}^{2}=0.11\pm 0.01\ll 1$$ E 2 = 0.11 ± 0.01 ≪ 1 . The modes display − 7.7 ± 0.5 dB of two-mode squeezing and an overall state purity of 0.63 ± 0.16. EPR-steering is observed over five octaves of sideband frequencies from RF down to audio-band. The demonstrated combination of high state purity, strong quantum correlations, and extended frequency range enables new matter-light quantum protocols.

Acoustic frequency atomic spin oscillator in the quantum regime

“…7 illustrates the expected broadband noise reduction in the GWD signal below the SQL obtained by combining the spin ensemble and the entangled light source demonstrated in Ref. [20]. The dark red curve represents the case of quantum cooperativity C q = 40, corresponding approximately to the ratio between readout rate Γ S and power broadening contribution to the decoherence rate γ S,pb in the present experiment, while assuming the absence of thermal noise n S = 0 and negligible intrinsic linewidth γ S,0 γ S,pb .…”

“…As proposed in Refs. [18,19], combining a GWD with a negative-mass spin oscillator using a recently demonstrated two-color source of entangled light [20] allows for cancellation of both shot noise and QBA noise, enabling broadband sensitivity beyond the SQL. QBA-free sensing in the acoustic frequency range would enable new sensing applications beyond SQL.…”

Towards quantum-enhanced Raman spectroscopy for bioimaging applications

“…While several different quantum states of light can, in principle, be used to provide such a quantum advantage, so far, it is only the ubiquitous squeezed states of light that have been demonstrated to be beneficial in practice [5][6][7][8] due to their generation simplicity and relative brightness. Quantum enhancement can be useful for measurements of extremely weak signals, with the crowning example being the detection of gravitational waves [9][10]. One field that can greatly benefit from sub-shot-noise detection is Raman spectroscopy of bio-samples.…”