Thrust V: Quantum repeater optical control network.

  • Impact on original proposal. We propose to direct supplemental resources to advance the conversion of the quantum repeater network prototype encompassed in our current research program, into a fully-controllable hybrid classical/quantum optical network. We envision to build a system in which entanglement swapping and distribution are controlled by optical signals, setting the optical paths and distributing time and control sequences among all the nodes and subsystems comprising the quantum repeater network. The main characteristics that we will developed in conjunction to the controlling hardware are the following:

 Concept of a controlling optical network directing entanglement swapping operations.} Entanglement swapping between nodes A and B is achieved by: (i) controlling the timing of entanglement generation in substations 1 and 3 directed by a main fast network controller, (ii) tracking the delivery of entanglement to Nodes A and B and substation 3 using updated-on-the-fly classical packets, iii) monitoring a successful Bell state measurement in substation 3 and iv) verification of entanglement delivery.

  • Deployment of optical switches in the main fiber exchange points and implementation of software defined network protocols, to direct the flow of entangled photons. A possible pathway is to use software similar in functionality to ESnet’s On-Demand Secure Circuits and Advanced Reservation System (OSCARS) to establish the initial quantum network topology.
  • Distribution of a clock signal optically, with nanosecond-level stabilization of internal clocks in every subsystem. We will construct this synchronization network using long distance clock-sharing systems using the White Rabbit optical precision time protocol. These systems will then be used as Stratum-0 timekeeping devices to synchronize the clocks of Stratum-1 servers co-located with the quantum hardware.
  • Implementing optical distribution of synchronized control signals to all quantum hardware modules using a centralized main FPGA-based controller and digital-to-optical transducers. Of most relevance is to provide time tagging for generated entangled pairs.
  • Implementation of entanglement tracking using synchronized, co-propagating packets containing the timing and updated status information of each entangled photon.
  • Implementation of quantum-measurement-based feedback to the main FPGA controller to indicate the status (Active/Non-active) of the quantum memory buffers in all substations and nodes.
  • Iterative monitoring of the status of all quantum memory buffers and coordination to identify four-fold detection events within the life time of the memories.
  • After a registered four-fold detection, implementation of live-monitoring of Bell state measurement results and repetition until success.
  • Monitoring of the distant quantum memory buffers states and verification of entanglement distribution.

Additional deliverable in Year 1: Deployment and testing of an optical control network with special functions geared towards entanglement swapping.

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