Zero-added-loss entanglement multiplexing using time-bin spectral shearing

TL;DR

The paper proposes a zero-added-loss multiplexing (ZALM) scheme for time-bin entanglement using spectral shearing to achieve deterministic frequency shifts without increasing loss. It develops a TBP-based optimization framework to maximize spectral-bin multiplexing and provides detailed analysis of drive-waveform effects and noise constraints. Experimental tests demonstrate compatibility between time-bin pulses and spectral shearing under appropriate drive conditions, supporting the feasibility of ZALM with time-bin qubits. The work suggests a practical path toward high-rate, memory-compatible entanglement distribution for quantum networks, while discussing filtering, memory integration, and potential hybrid implementations.

Abstract

High-quality quantum communications that enable important capabilities, such as distributed quantum computing and sensing, will require quantum repeaters for providing high-quality entanglement. To realize high-rate heralded entanglement for quantum repeaters, Chen et al. [Phys. Rev. Appl. 19, 054209 (2023)] proposed a scheme for heralded-multiplexed generation of quasi-deterministic entangled photon pairs, called zero-added-loss multiplexing (ZALM). Here, we propose a design of ZALM source using time-bin entanglement and spectral shearing. Additionally, we provide an analysis of experimentally relevant spectral-shearing parameters to optimize the spectral multiplexing. Moreover, we experimentally verify the compatibility of time-bin pulses and spectral shearing, as supported by observation of no phase shift when the same shearing is applied to both time bins. These results expand the benefits of applying a ZALM source to time-bin entanglement use cases. Moreover, more fully demonstrating time-bin and spectral shearing compatibility clears a path towards a broader use of spectral shearing that provides a deterministic frequency shift of high utility.

Figures (14)

• Figure 1: Proposed experimental setup to produce high-rate heralded entangled photons via the zero-added-loss multiplexing scheme. AM: amplitude modulator. AMP: RF amplifier. Atten: Attenuator. CIRC: fiber-optic circulator. EDFA: erbium-doped fiber amplifier. FF: feedforward. FBG: fiber-Bragg grating. FPGA: field-programmable gate array. HWP: half-wave plate. LCVR: liquid-crystal variable retarder. MBC: modulator-bias controller. PBS: polarizing-beamsplitter. PC: polarization controller. PD: photodiode. PG: pulse generator. PID: proportional-integral-derivative controller. PM: phase modulator. PMF: polarization-maintaining fiber. POL: polarizer. PRF: pump-reject filter. QWP: quarter-wave plate. RF: radio frequency. SHG: second-harmonic generation crystal. SMF: single-mode fiber. SNSPD: superconducting-nanowire single-photon detector. SPDC: spontaneous-parametric downconversion crystal. WDM: wavelength-division multiplexing. V: DC voltage source.
• Figure 2: Spectral-shearing parameter analysis for frequency-bin multiplexing optimization. Maximum number of allowed frequency bins versus spectral shearing (a) input RF power, (b) modulator $V_{\pi}$, and (c) input pulse time-bandwidth product. The different curves on each plot compare spectral-shearing drive waveform shapes: triangle wave, sawtooth wave, and sine wave. If not the variable along the X-axis, the simulation parameters used are: $P=10$ W; $V_{\pi}=1$ V; $\delta f_b=12.5$ GHz; $\Delta F_b=2$ GHz; $\Delta f \Delta t = 0.89$.
• Figure 3: Frequency-bin width analysis for spectral-shearing multiplexing. (a) maximum number of allowed frequency bins $n$ (b) spectral shearing drive frequency $D$ (c) pump repetition rate $R_p$ versus frequency-bin width $\delta f_b$. The different curves on each plot compare spectral-shearing drive waveform shapes: triangle wave, sawtooth wave, and sine wave. The simulation parameters used are: $\Delta F_b=2$ GHz; $\Delta f \Delta t = 0.89$.
• Figure 4: Spectral shearing time-domain analysis versus frequency-bin width. The simulation parameters used are: $\Delta F_b=2$ GHz; $\Delta f \Delta t = 0.89$.
• Figure 5: Joint-spectral analysis with filtering and pump bandwidth variation. Color bar units arbitrary. (a) Representative fiber-Bragg grating filter function for 12.5-GHz channels (O/E Land) and joint-spectral amplitude filtered as with the filter shown in (a) on each marginal for SPDC source modeled with Gaussian pump-envelop function using (b) 70-ps pump pulse duration and 12.9-GHz bandwidth and (c) 35-ps pump pulse duration and 25.8-GHz bandwidth and Sinc phase-matching function for periodically poled type-0 lithium niobate.