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High Speed Low Loss Quantum Optical Switch for 1550nm band



TECHNOLOGY AREA(S): Information Systems

OBJECTIVE: Develop and demonstrate a high speed low loss optical switch enabling high capacity quantum entanglement routing in fiber-based quantum networks.

DESCRIPTION: The Army is actively developing novel networks based on quantum phenomena, which will provide unprecedented degree of security and performance in challenging contested environments. Quantum mechanics permits nontrivial special connection between two or more physically separated systems that is called quantum entanglement. In quantum networks numerous pairs of entangled photons propagate over optical fibers to entangle remote network nodes. The resulting quantum entanglement between the nodes allows them to act in accord without explicitly exchanging any information. This in turn offers a number of novel functionalities, extending beyond those available to classical networks such as byzantine general agreement, multi-party function evaluations, quantum finger printing, and anonymous quantum communications. Testing and demonstrating these functionalities requires a small-scale operational quantum photonic network.

Many building blocks for quantum network (such as entanglement sources and detectors) have been researched, designed, built and even are available commercially. Yet a number of technological gaps remains. Some of these gaps – the design and development of hi-fidelity robust quantum memory units require advances in fundamental science. Yet there are the other areas for which the science had been well developed, and only the lack of deployable engineering solutions hinders the progress in quantum networking research and development. For instance, a crucial piece badly needed for putting together a quantum photonic network is a cascadable low-loss (< 1 dB), ultra-fast (GHz), fiber-based cross-bar switch, which would operate at 1550nm transparency window of optical fibers. This element will switch, route and time-bin entangled photon pairs for network operation [1].

The state-of-the-art fiber-optics switching solutions offered by telecom industry are either too slow (low-loss and low speed mechanical and MEMS switches) or have too much loss and polarization sensitivity (high speed and relatively high loss lithium niobate electro-optical switches). It is well understood in the community that low loss and high speed switches are possible to build utilizing the well-studied nonlinear optical phenomena in fibers [2,3]. Thus far such switches have been demonstrated, albeit near the 1300nm fiber transparency band. The switches operating in more technologically relevant (thought to be more challenging) 1550 nm transparency window are yet to be built. The engineering challenges here start with selection of appropriate component solutions for the pump laser and the nonlinear fiber, designing low loss pump/signal combiners, identifying suitable subsystem designs and testing components in out-of-spec ranges. More specifically, the trade-offs between the strength of chosen fiber nonlinearity, its dispersion and loss needs to be characterized to determine the optimal design. While challenging, this task does not require fundamentally new scientific approaches. Instead it calls for adapting existing technologies to the new wavelength range, which amounts to an effort in system engineering.

In summary, there is a need for the development of a quantum switch that operates in the 1550 nm band, has low loss (0.5 dB), high speed (10GHz band), and high fidelity when switching quantum signals. The switch characteristics should be suitable for cascaded operation, and must be demonstrated.

PHASE I: Investigate components to meet the project goals. Demonstrate the concept design. Show switching operation through laboratory testing, modeling, simulation and detailed calculations. Deliverable specification should include loss not exceeding 1dB over 10GHz band and extinction ratios of 13dB in pulsed configuration. Consider the impact of cascaded operation on the isolation of spurious photons. Prepare a plan for prototype development and verification of the planned specifications.

PHASE II: Demonstrate, characterize and deliver a prototype switch. Deliverable specification should include the fidelity of a quantum signal through a single and through cascaded switches to be above 90% for room temperature operation; the switching gate of 50ps; background Raman noise level of 1e-5 photons/gate; and overall insertion loss of 0.5dB. Determine the exact operating signal wavelength range. Extend the system to other relevant wavelength bands if possible.

PHASE III DUAL USE APPLICATIONS: Improving the prototype toward commercialization. The contractor should work with Army scientists and engineers, along with commercial partners, to identify and implement technology transition to military (ARMDEC, ECBC & CERDEC) and civilian applications (Datacom providers). The applications could impact many areas where the temporal resolution of sensitive light detectors are important including imaging through turbid media, laser radar, fluorescence lifetime imaging, and deep space optical communications (high sensitivity pulse position modulation receivers). Another potential application domain is Datacom, which needs for a cost-effective fast optical packet switch for future intra-data center networks.


  • Migdall, A. L., D. Branning, and S. Castelletto. "Tailoring single-photon and multiphoton probabilities of a single-photon on-demand source." Physical Review A 66.5 (2002): 053805.
  • Hall, Matthew A., Joseph B. Altepeter, and Prem Kumar. "Ultrafast switching of photonic entanglement." Physical review letters 106.5 (2011): 053901.
  • Rambo, Timothy M., et al. "Low-loss all-optical quantum switching." Photonics Society Summer Topical Meeting Series, 2013 IEEE. IEEE, 2013.

KEYWORDS: quantum networks, entanglement, fiber-optics, switching, routing


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