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Optimization of the time-multiplexed SPDC source at 900-950 nm range

V. O. Gotovtsev, I. V. Dyakonov, O. V. Borzenkova, K. A. Taratorin, T. B. Dugarnimaev, A. A. Korneev, S. P. Kulik, S. S. Straupe

TL;DR

This work demonstrates a time-multiplexed heralded single-photon source based on spontaneous parametric down-conversion in the 900–950 nm range, and analyzes how joint spectral amplitude, heralding efficiency, and purity govern performance. Using a ppKTP crystal and a Gaussian pump, the authors model the JSA/JSI to quantify heralding probability and purity, and they derive compact expressions linking these metrics to focal parameters. Time multiplexing with a memory and FPGA-controlled switching is shown to increase the probability of delivering a single photon within a temporal window, with experimental data indicating significant gains after about 16 multiplexed modes and a heralding efficiency around 0.31–0.34 in practice. The study also highlights the trade-offs between purity and heralding efficiency, and proposes domain-engineering of the nonlinear crystal as a route to higher purity without sacrificing brightness, offering practical guidance for scalable, high-performance SPDC-based HSPS implementations.

Abstract

In the field of quantum technology, single photons have emerged as a pivotal resource, prompting the development of heralded single photon sources (HSPS) with enhanced generation probability. The majority of such sources are based on spontaneous parametric down-conversion (SPDC), but they exhibit a low single photon generation probability. The multiplexing principle (arXiv:quant-ph/0205103) has been proposed as a solution to this problem. This paper presents a demonstration of a time-multiplexed HSPS based on the SPDC process, including accurate calculations and modeling of key source characteristics, specifically purity and heralding efficiency. Furthermore, the paper provides an analysis and approximation of the probability of a single photon post-application of time multiplexing.

Optimization of the time-multiplexed SPDC source at 900-950 nm range

TL;DR

This work demonstrates a time-multiplexed heralded single-photon source based on spontaneous parametric down-conversion in the 900–950 nm range, and analyzes how joint spectral amplitude, heralding efficiency, and purity govern performance. Using a ppKTP crystal and a Gaussian pump, the authors model the JSA/JSI to quantify heralding probability and purity, and they derive compact expressions linking these metrics to focal parameters. Time multiplexing with a memory and FPGA-controlled switching is shown to increase the probability of delivering a single photon within a temporal window, with experimental data indicating significant gains after about 16 multiplexed modes and a heralding efficiency around 0.31–0.34 in practice. The study also highlights the trade-offs between purity and heralding efficiency, and proposes domain-engineering of the nonlinear crystal as a route to higher purity without sacrificing brightness, offering practical guidance for scalable, high-performance SPDC-based HSPS implementations.

Abstract

In the field of quantum technology, single photons have emerged as a pivotal resource, prompting the development of heralded single photon sources (HSPS) with enhanced generation probability. The majority of such sources are based on spontaneous parametric down-conversion (SPDC), but they exhibit a low single photon generation probability. The multiplexing principle (arXiv:quant-ph/0205103) has been proposed as a solution to this problem. This paper presents a demonstration of a time-multiplexed HSPS based on the SPDC process, including accurate calculations and modeling of key source characteristics, specifically purity and heralding efficiency. Furthermore, the paper provides an analysis and approximation of the probability of a single photon post-application of time multiplexing.
Paper Structure (8 sections, 28 equations, 12 figures)

This paper contains 8 sections, 28 equations, 12 figures.

Table of Contents

  1. Introduction
  2. Joint spectral amplitude
  3. Heralding efficiency and Purity
  4. Time multiplexing
  5. Experiment
  6. Conclusion
  7. Appendix A
  8. Appendix B

Figures (12)

  • Figure 1: (a) The pump spectral envelope function -- $s(\omega_p=\omega_s+\omega_i)$; (b) The phase mismatch function module -- $|\Phi|$; (c) Joint spectral intensity -- $|\psi(\omega_s,\omega_i)|^2$
  • Figure 2: Heralding efficiency dependence of wavelength (a) -- signal heralding efficiency, (b) -- idler heralding efficiency, (c) -- symmetric heralding efficiency
  • Figure 3: (a) Symmetric heralding efficiency dependence of pump and signal/idler focal parameters. (b) Maximum JSI value depending on focal parameters. Red dot corresponds to $\xi_p=\xi_s=\xi_i\approx 0.55$ that we got in our model. The red marker corresponds to the optimum values $\xi_p=\xi_s=\xi_i\approx 2.84$
  • Figure 4: Purity (green line) and normalized value of heralding efficiency (blue and orange lines) versus filters width
  • Figure 5: Time multiplexing scheme. We pump nonlinear crystal with a period $\tau$ and probabilistically generate photon pare during different N time bins. With detecting idler photons we put into the time storage the last heralded signal photon and output it after considered N time bins.
  • ...and 7 more figures