Quantum-correlated Photon Pairs Research Articles

Quantum-correlated photon pairs generated in a commercial 45 nm complementary metal-oxide semiconductor microelectronic chip

Correlated photon pairs are a fundamental building block of quantum photonic systems. While pair sources have previously been integrated on silicon chips built using customized photonics manufacturing processes, these often take advantage of only a small fraction of the established techniques for microelectronics fabrication and have yet to be integrated in a process that also supports electronics. Here we report the first demonstration of quantum-correlated photon pair generation in a device fabricated in an unmodified advanced (sub-100-nm) complementary metal-oxide semiconductor (CMOS) process, alongside millions of working transistors. The microring resonator photon pair source is formed in the transistor layer structure, with the resonator core formed by the silicon layer typically used for the transistor body. With ultralow CW on-chip pump powers ranging from 4.8 to 400 μW, we demonstrate pair generation rates between 165 Hz and 332 kHz using >80% efficient WSi superconducting nanowire single-photon detectors. Coincidences-to-accidentals ratios consistently exceeding 40 were measured, with a maximum of 55. In the process of characterizing this source, we also accurately predict pair generation rates from the results of classical stimulated four-wave mixing measurements. This proof-of-principle device demonstrates the potential of commercial CMOS microelectronics as an advanced quantum photonics platform with the capability of large volumes and pristine process control, where state-of-the-art high-speed digital circuits could interact with quantum photonic circuits.

基于不同种类光纤的量子关联光子对源输出特性比较

基于不同种类光纤的量子关联光子对源输出特性比较

Integrated Source of Spectrally Filtered Correlated Photons for Large-Scale Quantum Photonic Systems

We demonstrate the generation of quantum-correlated photon-pairs combined with the spectral filtering of the pump field by more than 95dB using Bragg reflectors and electrically tunable ring resonators. Moreover, we perform demultiplexing and routing of signal and idler photons after transferring them via a fiber to a second identical chip. Non-classical two-photon temporal correlations with a coincidence-to-accidental ratio of 50 are measured without further off-chip filtering. Our system, fabricated with high yield and reproducibility in a CMOS process, paves the way toward truly large-scale quantum photonic circuits by allowing sources and detectors of single photons to be integrated on the same chip.

Stimulated Emission Tomography

We identify a relation between the number of photon pairs generated by parametric fluorescence, through either spontaneous parametric down-conversion (SPDC) or spontaneous four-wave mixing, and the number generated by the corresponding stimulated process, respectively, either difference-frequency generation or stimulated four-wave mixing. On the basis of this very general result, we show that the characterization of SPDC sources of two-photon states in a given system can be performed solely by studying stimulated emission. We call this technique stimulated emission tomography (SET). We show that the number of photons detected in SET can be 9 orders of magnitude larger than the average number of coincidence counts in two-photon quantum state tomography. These results open the way to the study of sources of quantum-correlated photon pairs with unprecedented precision and unparalleled resolution.

Slow light enhanced correlated photon pair generation in photonic-crystal coupled-resonator optical waveguides

We demonstrate the generation of quantum-correlated photon pairs from a Si photonic-crystal coupled-resonator optical waveguide. A slow-light supermode realized by the collective resonance of high-Q and small-mode-volume photonic-crystal cavities successfully enhanced the efficiency of the spontaneous four-wave mixing process. The generation rate of photon pairs was improved by two orders of magnitude compared with that of a photonic-crystal line defect waveguide without a slow-light effect.

全光纤便携式量子关联光子对源

全光纤便携式量子关联光子对源

Role of Absorption on the Generation of Quantum-Correlated Photon Pairs Through FWM

The impact of fiber absorption on the generation rate of quantum-correlated photon pairs through spontaneous four-wave mixing in optical fibers is studied theoretically. We quantify the impact of the loss through the analysis of the Cauchy-Schwarz correlation parameter and the Clauser, Horne, Shimony, and Holt inequality. Results show that fiber loss can improve the quantum-correlation between the photon pairs. This is a consequence of the decrease of the individual signal and idler photon-fluxes, which reduces the rate of uncorrelated photons generated through Raman scattering inside the optical fiber. Findings show that a high degree of polarization entanglement is obtained when the ratio of signal to idler photon-fluxes lies between 0.5 and 0.8, in a regime with high losses on the signal wave.

Quantum-correlated photon pair generation in tellurite microstructured optical fibers

We theoretically investigated the generation of quantum-correlated photon pair through spontaneous four-wave mixing in tellurite microstructured optical fiber (MOF). We evaluated the performance of photon pair generation in tellurite fibers based on Raman gain coefficient spectra. It was shown that the TBSN16P6W tellurite fiber provided a low Raman noise on correlation photon generation over a wide pump-idler detuning range. We can choose proper tellurite composition to obtain a low Raman gain window over wide range for correlated photon pair generation. We also designed the tellurite MOF structure to obtain a small dispersion value with high nonlinear coefficient at telecommunication wavelengths, thus realize efficient quantum-correlated photon pair generation.

Generation of high purity quantum correlated photon pairs based on photonic crystal fiber

A one-meter-long high nonlinear photonic crystal fiber is pumped by laser pulse train at room temperature, and the generated correlated idler and signal photons are centred at 830 nm and 1411 nm, respectively. The full widths at half maximum of the broad band filters of the two channel are 15 nm and 35 nm, respectively. The fitting results of single channel photon counts reveal that almost all the photons originate from spontaneous four wave mixing and the influence of Raman scattering is eliminated. When the production rate is 0.0085 photon per pulse, the ratio between coincidence rate and accidental coincidence rate is measured to be 102, which not only confirms the low noise property of the photon pair, but also shows that the photon pair are naturally narrow band, and the collecting efficiency in our experiment is high. Moreover, these high purity photon pairs connect different optical bands, and have potential applications in quantum information technologies.

利用高非线性光纤产生量子关联光子对的实验研究

利用高非线性光纤产生量子关联光子对的实验研究

Efficient two-step up-conversion by quantum-correlated photon pairs

We theoretically investigate the sequential two-step upconversion of correlated photon pairs with positive and negative energy correlations, in terms of how the up-conversion efficiency depends on the incident pulse delay. A three-level atomic system having a metastable state is used to evaluate the up-conversion efficiency. It is shown that a photon pair with a positive energy correlation can drastically enhance the up-conversion efficiency compared with uncorrelated photons and correlated photons with a negative energy correlation.

Quantum-correlated photon pair generation in chalcogenide As_2S_3 waveguides

We theoretically investigate the generation of quantum-correlated photon pairs through spontaneous four-wave mixing in chalcogenide As(2)S(3) waveguides. For reasonable pump power levels, we show that such photonic-chip-based photon-pair sources can exhibit high brightness (approximately 1 x 10(9) pairs/s) and high correlation (approximately 100) if the waveguide length is chosen properly or the waveguide dispersion is engineered. Such a high correlation is possible in the presence of Raman scattering because the Raman profile exhibits a low gain window at a Stokes shift of 7.4 THz, though it is constrained due to multi-pair generation. As the proposed scheme is based on photonic chip technologies, it has the potential to become an integrated platform for the implementation of on-chip quantum technologies.

Photonic Crystal Fiber Source of Quantum Correlated Photon Pairs in the 1550 nm Telecom Band

A source of quantum correlated photon pairs in the 1550nm telecom band obtained by a pumping 11m photonic crystal fiber with 10 ps pulse trains is experimentally demonstrated. We investigate how the birefringence of the fiber influences the purity of the photon pairs. We also present the frequency correlation of the signal and idler photon pairs. The experimental results are useful for developing a compact source of photon pairs well suited for quantum communication.

Quantum Key Distribution Network Based on Differential PhaseShift

Using a series of quantum correlated photon pairs, we propose atheoretical scheme for any-to-any multi-user quantum keydistribution network based on differential phase shift. Thedifferential phase shift and the different detection time slotsensure the security of our scheme against eavesdropping. We discussthe security under the intercept–resend attack and the sourcereplacement attack.

Silicon waveguides for creating quantum-correlated photon pairs

We propose to use four-wave mixing inside silicon waveguides for generating quantum-correlated photon pairs in a single spatial mode. Such silicon-based photon sources not only exhibit high pair correlation but also have high spectral brightness. As the proposed scheme is based on mature silicon technology, it has the potential of becoming a cost-effective platform for on-chip quantum information processing applications.

Quantum key distribution using a series of quantum correlated photon pairs

The differential-phase-shift quantum key distribution (DPS-QKD) is a recently proposed QKD scheme in which a pulse train is transmitted through a quantum channel. This paper extends the ideal of the DPS-QKD to entanglement-based systems. Two schemes are presented. In one, an entanglement source sends pulse trains of signal and idler to two parties (Alice and Bob), respectively, who phase-modulate the incoming pulses and receive them after one-bit delay interferometers. In the other, two entanglement sources are prepared, one between Alice and a repeating node (Charlie) and one between Charlie and Bob, which send signal and idler pulse trains to Alice and Bob and Charlie, respectively. These schemes offer a longer distance between Alice and Bob than the conventional DPS-QKD.

1.5-µm band quantum-correlated photon pair generation in dispersion-shifted fiber: suppression of noise photons by cooling fiber

Spontaneous four-wave mixing in a dispersion-shifted fiber (DSF) is a promising approach for generating quantum-correlated photon pairs in the 1.5 microm band. However, it has been reported that noise photons generated by the spontaneous Raman scattering process degrade the quantum correlation of the generated photons. This paper describes the characteristics of quantum-correlated photon pair generation in a DSF cooled by liquid nitrogen. With this technique, the number of noise photons was sufficiently suppressed and the ratio of true coincidence to accidental coincidence was increased to ~30.

Generation of Quantum-Correlated Photon Pairs in Optical Fiber: Influence of Spontaneous Raman Scattering

The generation of quantum-correlated photon pairs by spontaneous four-wave mixing (FWM) in an optical fiber is studied. After demonstrating the time correlation between signal and idler photons, the influence of spontaneous Raman scattering on extracting photon pairs is experimentally investigated. It is shown that a short pulse and a narrow filtering bandwidth are preferable for obtaining correlated photon pairs with a better signal-to-noise ratio via FWM in an optical fiber.

All-fiber photon-pair source for quantum communications

In this letter, we present a source of quantum-correlated photon pairs based on parametric fluorescence in a fiber Sagnac loop. The photon pairs are generated in the 1550-nm fiber-optic communication band and detected with InGaAs-InP avalanche photodiodes operating in a gated Geiger mode. A generation rate > 10/sup 3/ pairs/s is observed, which is limited by the detection electronics at present. We also demonstrate the nonclassical nature of the photon correlations in the pairs. This source, given its spectral properties and robustness, is well suited for use in fiber-optic quantum communication and cryptography networks.