Entanglement and nonlocality between disparate solid-state quantum memories mediated by photons

Abstract

operating at different wavelengths through the exchange of photons. However, so far, only a few investigations have been reported [16-18], and none of them has included a quantum memory functioning at telecommunication wavelength. In this work, we demonstrate entanglement between two atomic frequency comb (AFC)-based quantum memories [19] in ensembles of cryogenically cooled rare-earth ions, one for 794-nmand one for 1535-nm-wavelength photons. The first memory employs a thulium-doped lithium-niobate (Tm 3+ :LiNbO 3) crystal, the second an erbium-doped fiber (Er 3+ :SiO 2). Entanglement is created through the interaction with entangled photons created by spontaneous parametric down-conversion. Both memories allow buffering and re-emitting multiplexed quantum data in feed-forward-controlled spectral or temporal modes, either of which makes them suitable for quantum repeaters [20,21]. It is significant that our experiment involves two classes of ions: Kramers and non-Kramers. Due to their specific electronic configurations, Kramers ions are strongly coupled to the local magnetic environment while non-Kramers ions are relatively immune to magnetic-field fluctuations. These characteristics make Kramers ions strong candidates for quantum sensors while non-Kramers are generally more suitable for quantum memory with long storage time.

Defect Engineering for Quantum Grade Rare-Earth Nanocrystals

“…Hours long T 2 have even been observed when control techniques to decrease perturbations from the ions' environment are applied 7 . These outstanding properties have led to many demonstrations in the field of quantum memories for light including long time storage of single photons 8 , photonic entanglement storage 9 , and light to matter teleportation 10 . At the nanoscale, new possibilities appear based on coupling to optical and microwave micro-or nano-cavities for greatly enhanced interactions with light or accessing extreme sensitivities together with nanometer spatial resolution [11][12][13][14][15] .…”

Nonclassical Effects Based on Husimi Distributions in Two Open Cavities Linked by an Optical Waveguide

“…Entanglement is a specific kind of quantum correlations, and has been extensively studied for many systems [ 20 , 22 , 23 , 24 , 25 , 26 ]. It is linked to several applications in quantum information, such as quantum processing [ 27 ], key distribution [ 28 ], teleportation [ 29 ], cryptography [ 30 ], and quantum memory [ 31 , 32 ].…”

Long-Lived Solid-State Optical Memory for High-Rate Quantum Repeaters

“…After passing through the crystal's h110i direction, the light is directed to a photodetector. This setup is used for AFC creation (see also [38]), initial memory characterization, and storage of optical pulses in a single spectral mode. For frequencymultiplexed storage and feed-forward recall, additional phase modulators are used to add frequency sidebands to the laser light, each of which creates a memory in a different spectral segment, and to frequency shift the light after reemission so that only the desired spectral mode passes through an optical filter cavity [6].…”

“…To this end, we used 1-μs-long laser pulses (note that the use of true single photons would not change the results), and created AFCs with finesse F-the ratio between AFC peak spacing Δ and peak width δ-of 2. See [6,38] for more information. Tooth spacings varied between 100 and 10 kHz, corresponding to storage times between 10 and 100 μs, respectively.…”