Single-photon Frequency Conversion Research Articles

Controllable nonreciprocal single-photon frequency converter via a four-level system

We propose an efficient, nonreciprocal single-photon device that achieves single-photon routing and frequency conversion through chiral coupling of two one-dimensional waveguides with a four-level atom. Photons incoming from one port can be definitely directed to another port. However, the photon frequency conversion has been achieved only when the single photons are transferred from one waveguide to the other, and its probability can reach unity. Applied the on-demand classical field to drive an atom, the transmission quantum tunneling path can be turned off and on by exploiting the Autler–Townes splitting mechanism. Our results illustrate the potential of our device for applications in a quantum network.

Two‐Stage, Low Noise Quantum Frequency Conversion of Single Photons from Silicon‐Vacancy Centers in Diamond to the Telecom C‐Band

AbstractThe silicon‐vacancy center in diamond holds great promise as a qubit for quantum communication networks. However, since the optical transitions are located within the visible red spectral region, quantum frequency conversion to low‐loss telecommunication wavelengths becomes a necessity for its use in long‐range, fiber‐linked networks. This work presents a highly efficient, low‐noise quantum frequency conversion device for photons emitted by a silicon‐vacancy (SiV) center in diamond to the telecom C‐band. By using a two‐stage difference‐frequency mixing scheme, spontaneous parametric down‐conversion (SPDC) noise is circumvented and Raman noise is minimized, resulting in a very low noise rate of 10.4 ± 0.7 photons per second as well as an overall device efficiency of 35.6%. By converting single photons from SiV centers, it demonstrates the preservation of photon statistics upon conversion.

Ultratunable Quantum Frequency Conversion in Photonic Crystal Fiber.

Quantum frequency conversion of single photons between wavelength bands is a key enabler to realizing widespread quantum networks. We demonstrate the quantum frequency conversion of a heralded 1551nm photon to any wavelength within an ultrabroad (1226-1408nm) range in a group-velocity-symmetric photonic crystal fiber, covering over 150 independent frequency bins. The target wavelength is controlled by tuning only a single pump laser wavelength. We find internal, and total, conversion efficiencies of 12(1)% and 1.4(2)%, respectively. For the case of converting 1551 to 1300nm we measure a heralded g^{(2)}(0)=0.25(6) for converted light from an input with g^{(2)}(0)=0.034(8). We expect that this photonic crystal fiber can be used for myriad quantum networking tasks.

Tunable and state-preserving frequency conversion of single photons in hydrogen.

In modern quantum technologies, preservation of the photon statistics of quantum optical states upon frequency conversion holds the key to the viable implementation of quantum networks, which often require interfacing of several subsystems operating in widely different spectral regions. Most current approaches offer only very small frequency shifts and limited tunability, while suffering from high insertion loss and Raman noise originating in the materials used. We introduce a route to quantum-correlation-preserving frequency conversion using hydrogen-filled antiresonant-reflecting photonic crystal fibers. Transient optical phonons generated by stimulated Raman scattering enable selective frequency up-conversion by 125 terahertz of the idler photon of an entangled pair, with efficiencies up to 70%. This threshold-less molecular modulation process preserves quantum correlations, making it ideal for applications in quantum information.

Group-velocity symmetry in photonic crystal fibre for ultra-tunable quantum frequency conversion

Low-noise frequency conversion of single photons is a critical tool in establishing fibre-based quantum networks. We show that a single photonic crystal fibre can achieve frequency conversion by Bragg-scattering four-wave mixing of source photons from an ultra-broad wavelength range by engineering a symmetric group velocity profile. Furthermore, we discuss how pump tuning can mitigate realistic discrepancies in device fabrication. This enables a single highly adaptable frequency conversion interface to link disparate nodes in a quantum network via the telecoms band.

Improving entanglement generation rates in trapped-ion quantum networks using nondestructive photon measurement and storage

Long range quantum information processing will require the integration of different technologies to form hybrid architectures combining the strengths of multiple quantum systems. In this work, we propose a hybrid networking architecture designed to improve entanglement rates in quantum networks based on trapped ions. Trapped ions are excellent candidates as network nodes but photon losses make long-distance networking difficult. To overcome some losses and extend the range of trapped-ion-based networks, we propose including neutral-atom-based non-destructive single-photon detection and single photon storage in between networking nodes, forming a hybrid network. This work builds on recently demonstrated optical frequency conversion of single photons emitted by trapped ions. We derive the average two-node entanglement rate for this proposed network architecture as a function of distance. Using reasonable experimental parameters, we show this proposed quantum network can generate remote entanglement rates up to a factor of 100 larger than that of an equivalent homogeneous network at both near-IR and C-band wavelengths for distances up to 50 km.

Quantum Frequency Conversion of Single Photons from a Nitrogen-Vacancy Center in Diamond to Telecommunication Wavelengths

We report on the conversion to telecom wavelength of single photons emitted by a nitrogen-vacancy (NV) defect in diamond. By means of difference frequency generation, we convert spin-selective photons at 637 nm, associated with the coherent NV zero-phonon-line, to the target wavelength of 1588 nm in the L-telecom band. The successful conversion is evidenced by time-resolved detection revealing a telecom photon lifetime identical to that of the original 637 nm photon. Furthermore, we show by second-order correlation measurements that the single-photon statistics are preserved. The overall efficiency of this one-step conversion reaches 17\% in our current setup, along with a signal-to-noise ratio of $\approx$7 despite the low probability $(< 10^{-3})$ of an incident 637 nm photon. This result shows the potential for efficient telecom photon - NV center interfaces and marks an important step towards future long-range entanglement-based quantum networks.

Single-photon frequency conversion via cascaded quadratic nonlinear processes

Frequency conversion of single photons is an important technology for quantum interface and quantum communication networks. Here, single-photon frequency conversion in the telecommunication band is experimentally demonstrated via cascaded quadratic nonlinear processes. Using cascaded quasi-phase-matched sum and difference frequency generation in a periodically poled lithium niobate waveguide, the signal photon of a photon pair from spontaneous down-conversion is precisely shifted to identically match its counterpart, i.e., the idler photon, in frequency to manifest a clear nonclassical dip in the Hong-Ou-Mandel interference. Moreover, quantum entanglement between the photon pair is maintained after the frequency conversion, as is proved in time-energy entanglement measurement. The scheme is used to switch single photons between dense wavelength-division multiplexing channels, which holds great promise in applications in realistic quantum networks.

Temporally and spectrally multiplexed single photon source using quantum feedback control for scalable photonic quantum technologies

Current proposals for scalable photonic quantum technologies require on-demand sources of indistinguishable single photons with very high efficiency. Even with recent progress in the field there is still a significant gap between the requirements and state of the art performance. Here, we propose an on-chip source of time-multiplexed, heralded photons. Using quantum feedback control on a photon storage cavity with an optimized driving protocol, we estimate an on-demand efficiency of 99% and unheralded loss of order 1%, assuming high efficiency detectors and intrinsic cavity quality factors of order 108. We further explain how temporal- and spectral-multiplexing can be used in parallel to significantly reduce device requirements if single photon frequency conversion is possible with efficiency in the same range of 99%.

Single-photon frequency conversion for generation of three-dimensional entanglement

A single-photon frequency conversion scheme is proposed to generate three-dimensional entanglement between a quantum emitter and a photon with different frequencies. In the scheme, after scattered by a four-level quantum emitter on Sagnac loop, input photon is divided into three parts and each has its own frequency via constructive interference. In addition, through tuning system parameters, we can achieve equal probability amplitudes of output photons which mean the realization of three-dimensional entanglement. Our calculations show that the present scheme is robust against the deviation of experimental and decoherence.

Nonreciprocal Single Photon Frequency Conversion via Chiral Coupling between a V-Type System and a Pair of Waveguides**Supported by the Anhui Provincial Natural Science Foundation under Grant No 1608085MA09, and the National Natural Science Foundation of China under Grant Nos 11774262, 61675006, 11474003 and 61472282.

The single photon frequency conversion is investigated theoretically in the system composed of a V-type system chiral coupling to a pair of waveguides. The single photon scattering amplitudes are obtained using the real-space Hamiltonian. The calculated results show that the probability of single photon frequency down- or up-conversion can reach a unit by choosing appropriate parameters in the non-dissipative system with perfect chiral coupling. We present a nonreciprocal single photon beam splitter whose frequency of the output photon is different from that of the input photon. The influences of dissipations and non-perfect chiral coupling on the single frequency conversion are also shown. Our results may be useful in designing quantum devices at the single-photon level.

Nonreciprocal single-photon frequency converter via multiple semi-infinite coupled-resonator waveguides

We propose to construct a nonreciprocal single-photon frequency converter via multiple semi-infinite coupled-resonator waveguides (CRWs). We first demonstrate that the frequency of a single photon can be converted nonreciprocally through two CRWs, which are coupled indirectly by optomechanical interactions with two nondegenerate mechanical modes. Based on such nonreciprocity, two different single-photon circulators are proposed in the T-shaped waveguides consisting of three semi-infinite CRWs, which are coupled in pairwise by optomechanical interactions. One circulator is proposed by using two nondegenerate mechanical modes and the other one is proposed by using three nondegenerate mechanical modes. Nonreciprocal single-photon frequency conversion is induced by breaking the time-reversal symmetry, and the optimal conditions for nonreciprocal frequency conversion are obtained. These proposals can be used to realize nonreciprocal frequency conversion of single photons in any two distinctive waveguides with different frequencies and they can allow for dynamic control of the direction of frequency conversion by tuning the phases of external driving lasers, which may have versatile applications in hybrid quantum networks.

Efficient single-photon frequency conversion in the microwave domain using superconducting quantum circuits

We present an approach to achieve efficient single-photon frequency conversion in the microwave domain based on coherent control in superconducting quantum circuits, which consist of a driven artificial atom coupled to a semi-infinite transmission line. Using the full quantum-mechanical method, we analyze the single-photon scattering process in this system and find that single-photon frequency up- or down-conversion with efficiency close to unity can be achieved by adjusting the parameters of the control field applied to the artificial atom. We further show that our approach is experimentally feasible in currently available superconducting flux qubit circuits.

Single-photon frequency conversion via interaction with a three-level atom coupled to a microdisk

The frequency conversion of light has proved to be an important instrument for communication, spectroscopy, imaging and information processing. We theoretically study the frequency conversion of a single photon via its interaction with a -type atom coupled to a microdisk. We show that the frequency conversion efficiency approaches unity even in the case of an interaction between clockwise and counterclockwise modes in the microdisk due to surface imperfections. By the use of the Schrieffer–Wolff transformation, we get an effective Hamiltonian that allows us to investigate the dynamics of the system and obtain time and probability of frequency conversion in different conditions.

Frequency conversion between UV and telecom wavelengths in a lithium niobate waveguide for quantum communication with Yb+ trapped ions

We study and demonstrate the frequency conversion of UV radiation, resonant with 369.5 nm transition in Yb+ ions to the C-band wavelength 1580.3 nm and vice-versa using a reverse proton-exchanged waveguide in periodically poled lithium niobate. Our integrated device can interface trapped Yb+ ions with a telecom infrastructure for the realization of an Yb+ based quantum repeater protocol and to efficiently distribute entanglement over long distances. We analyse the single photon frequency conversion efficiency from the 369.525 nm to the telecom wavelength and its dependence on pump power, device length and temperature. The single-photon noise generated by the spontaneous Raman scattering of the pump is also measured. From this analysis we estimate a single photon conversion efficiency of ∼9% is achievable with our technology with almost complete suppression of the Raman noise.

Single-photon frequency conversion and multi-mode entanglement via constructive interference on Sagnac loop

Based on constructive interference in Sagnac waveguide loop, an efficient scheme is proposed for selective frequency conversion and multifrequency modes W entanglement via input–output formalism. We can adjust the probability amplitudes of output photons by choosing parameter values properly. The tunable probability amplitude will lead to the generation of output photon with a selectable frequency and W photonic entanglement of different frequencies modes in a wide range of parameter values. Our calculations show the present scheme is robust to the deviation of parameters and spontaneous decay.

Optimizing optical Bragg scattering for single-photon frequency conversion

We develop a systematic theory for optimising single-photon frequency conversion using optical Bragg scattering. The efficiency and phase-matching conditions for the desired Bragg scattering conversion as well as spurious scattering and modulation instability are identified. We find that third-order dispersion can suppress unwanted processes, while dispersion above the fourth order limits the maximum conversion efficiency. We apply the optimisation conditions to frequency conversion in highly nonlinear fiber, silicon nitride waveguides and silicon nanowires. Efficient conversion is confirmed using full numerical simulations. These design rules will assist the development of efficient quantum frequency conversion between multicolour single photon sources for integration in complex quantum networks.

Scattering in the ultrastrong regime: nonlinear optics with one photon.

The scattering of a flying photon by a two-level system ultrastrongly coupled to a one-dimensional photonic waveguide is studied numerically. The photonic medium is modeled as an array of coupled cavities and the whole system is analyzed beyond the rotating wave approximation using matrix product states. It is found that the scattering is strongly influenced by the single- and multiphoton dressed bound states present in the system. In the ultrastrong coupling regime a new channel for inelastic scattering appears, where an incident photon deposits energy into the qubit, exciting a photon-bound state, and escaping with a lower frequency. This single-photon nonlinear frequency conversion process can reach up to 50% efficiency. Other remarkable features in the scattering induced by counterrotating terms are a blueshift of the reflection resonance and a Fano resonance due to long-lived excited states.

Ultra-wide single-photon frequency conversion and entanglement via constructive interference

We investigate theoretically a single-photon frequency conversion with a Sagnac waveguide loop by input-output formalism. The results show that an ultra-wide tunable frequency conversion can be achieved via constructive interference and a flexible adjustment of parameters. For instance, we discuss the generation of ultraviolet photons in detail, which corresponds to the up-conversion process of frequency. We also can obtain entangled states of photons and atoms under suitable parameter conditions. Our calculations prove that a single-photon frequency conversion with high efficiency can be realized, even if effected by spontaneous decay and deviation of parameters.

Controllable single-photon frequency converter via a one-dimensional waveguide

We propose a single-photon frequency converter via a one-dimensional waveguide coupled to a $V$-type atom. The on-demand classical field allows the atom to absorb a photon with a given frequency, then emit a photon with a carried frequency different from the absorbed one. The absorption and re-emission process is formulated as a two-channel scattering process. We study the single-photon frequency conversion mechanism in two kinds of realistic physical system: coupled resonator waveguide with cosine dispersion relation and an optical waveguide with linear dispersion relation respectively. We find that the driving field prefers weak in coupled resonator waveguide but arbitrarily strong in optical waveguide to achieve an optical transfer efficiency.