DOE SBIR Phase I Final Report: Deterministic High-Flux Single Photon Source for Quantum Networks
- Qubitekk, Inc.
One of the outstanding challenges for quantum networking and quantum communication is achieving high flux rates for single photons, considered to be foundational a resource for quantum networks. A deterministic single-photon source is one that produces single photons at regular times and in a well-defined spectral and spatial mode. Photon pair sources based on spontaneous parametric downconversion (SPDC) can be used as heralded single-photon sources, whereby the detection of one photon signals, or “heralds” the existence of the partner photon in a conjugate mode. However, these sources cannot achieve a high probability of producing a single photon without also increasing the probability of multi-pair emissions. This limitation can be overcome by multiplexing many individual heralded SPDC sources. When emission is detected from one source, the conjugate photon is routed to a single target output mode. In this way, the overall probability of a heralded photon can be made quite high, while the likelihood of multi-pair events from any given source can be held low. Demonstrations to date have included spatial, temporal, and spectral multiplexing approaches. An analysis of heralded SPDC shows that even a small number of heralded SPDC sources multiplexed to a common output can outperform a single heralded source and can approximate a deterministic single-photon source if enough multiplexed channels are included. For reasonable estimates of heralding efficiency, the analysis showed that hundreds of multiplexed channels will be required. The analysis also showed that, for a given target performance level, additional channels would be required to offset any optical losses or operational inefficiencies in the multiplexed system. In addition to these general considerations, it will also be important to achieve spectrally pure photons in the output mode. These three important results provide the design principles that should guide the development of any single-photon source based on multiplexed SPDC: a) Any technology incorporated into a multiplexed SPDC system must be conducive to scaling to hundreds of multiplexed channels; b) Design choices should favor high heralding efficiency, high switching efficiency, and low optical losses; and c) Designs must be compatible with methods for generating spectrally pure output photons. Spectral multiplexing offers several clear advantages over spatial and temporal multiplexing. Several technical options are available for the three primary sub-systems in a spectrally multiplexed system: photon pair generation; wavelength-dependent heralding; and wavelength conversion to shift the heralded photons to the target output wavelength. Many of the important functions have been demonstrated previously, though not in a single scalable system. Nevertheless, this work provides strong evidence that a single-photon source based on several hundred spectrally multiplexed SPDC channels is technically feasible. In the context of the design principles noted above, a spectrally-multiplexed SPDC system for heralded single photons offers the following advantages: a single SPDC source can easily support hundreds or even thousands, of distinct spectral channels, more than enough to achieve single-photon source characteristics; a dispersive fiber spectrometer can provide nearly lossless spectral heralding; and nonlinear optical techniques provide a means of shifting the heralded photons to the output mode without passing the single photons through the lossy electro-optic modulators used in the temporal and spatial multiplexing approaches.
- Research Organization:
- Qubitekk, Inc.
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- SC0020538
- OSTI ID:
- 1768329
- Type / Phase:
- SBIR (Phase I)
- Report Number(s):
- DOE-Qubitekk-140FRPT
- Country of Publication:
- United States
- Language:
- English
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