Single-photon-triggered spin squeezing with decoherence reduction in optomechanics via phase matching

Abstract On-chip bright quantum sources with multiplexing ability are extremely high in demand for the integrated quantum networks with unprecedented scalability and complexity. Here, we demonstrate an ultrabright and broadband biphoton quantum source generated in a lithium niobate microresonator system. Without introducing the conventional domain poling, the on-chip microdisk produces entangled photon pairs covering a broad bandwidth promised by natural phase matching in spontaneous parametric down conversion. Experimentally, the multiplexed photon pairs are characterized by 30 nm bandwidth limited by the filtering system, which can be furthered enlarged. Meanwhile, the generation rate reaches 5.13 MHz/μW with a coincidence-to- accidental ratio up to 804. Besides, the quantum source manifests the prominent purity with heralded single photon correlation g(2)H(0)=0.0098±0.0021 and energy-time entanglement with excellent interference visibility of 96.5%±1.9%.

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Phase Matching Quantum Key Distribution based on Single-Photon Entanglement

Scientific Reports ◽

10.1038/s41598-019-51848-9 ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 1

Author(s):

Wei Li ◽

Le Wang ◽

Shengmei Zhao

Keyword(s):

Quantum Key Distribution ◽

Single Photon ◽

Key Distribution ◽

Phase Matching ◽

Single Photon Detection ◽

Beam Splitting ◽

Long Distance ◽

Photon Detection ◽

Security Proof ◽

Simulation Results

Abstract Two time-reversal quantum key distribution (QKD) schemes are the quantum entanglement based device-independent (DI)-QKD and measurement-device-independent (MDI)-QKD. The recently proposed twin field (TF)-QKD, also known as phase-matching (PM)-QKD, has improved the key rate bound from O(η) to O$$(\sqrt{{\boldsymbol{\eta }}})$$ ( η ) with η the channel transmittance. In fact, TF-QKD is a kind of MDI-QKD but based on single-photon detection. In this paper, we propose a different PM-QKD based on single-photon entanglement, referred to as single-photon entanglement-based phase-matching (SEPM)-QKD, which can be viewed as a time-reversed version of the TF-QKD. Detection loopholes of the standard Bell test, which often occur in DI-QKD over long transmission distances, are not present in this protocol because the measurement settings and key information are the same quantity which is encoded in the local weak coherent state. We give a security proof of SEPM-QKD and demonstrate in theory that it is secure against all collective attacks and beam-splitting attacks. The simulation results show that the key rate enjoys a bound of O$$(\sqrt{{\boldsymbol{\eta }}})$$ ( η ) with respect to the transmittance. SEPM-QKD not only helps us understand TF-QKD more deeply, but also hints at a feasible approach to eliminate detection loopholes in DI-QKD for long-distance communications.

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A metasurface-based diamond frequency converter using plasmonic nanogap resonators

Nanophotonics ◽

10.1515/nanoph-2020-0392 ◽

2020 ◽

Vol 10 (1) ◽

pp. 589-595

Author(s):

Qixin Shen ◽

Amirhassan Shams-Ansari ◽

Andrew M. Boyce ◽

Nathaniel C. Wilson ◽

Tao Cai ◽

...

Keyword(s):

Harmonic Generation ◽

Nonlinear Optical ◽

Quantum Communication ◽

Single Photon ◽

Second Harmonic ◽

Frequency Converter ◽

Phase Matching ◽

Third Harmonic ◽

Plasmonic Structures ◽

Raman Lasers

AbstractDiamond has attracted great interest as an appealing material for various applications ranging from classical to quantum optics. To date, Raman lasers, single photon sources, quantum sensing and quantum communication have been demonstrated with integrated diamond devices. However, studies of the nonlinear optical properties of diamond have been limited, especially at the nanoscale. Here, a metasurface consisting of plasmonic nanogap cavities is used to enhance both χ(2) and χ(3) nonlinear optical processes in a wedge-shaped diamond slab with a thickness down to 12 nm. Multiple nonlinear processes were enhanced simultaneously due to the relaxation of phase-matching conditions in subwavelength plasmonic structures by matching two excitation wavelengths with the fundamental and second-order modes of the nanogap cavities. Specifically, third-harmonic generation (THG) and second-harmonic generation (SHG) are both enhanced 1.6 × 107-fold, while four-wave mixing is enhanced 3.0 × 105-fold compared to diamond without the metasurface. Even though diamond lacks a bulk χ(2) due to centrosymmetry, the observed SHG arises from the surface χ(2) of the diamond slab and is enhanced by the metasurface elements. The efficient, deeply subwavelength diamond frequency converter demonstrated in this work suggests an approach for conversion of color center emission to telecom wavelengths directly in diamond.

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