Quantum Network Facility
Long-Distance Quantum Network Prototype
Long-Distance Matter-Matter Quantum Connections
The facility currently possesses one of the most advanced regional quantum networks in the US. The partnership between Brookhaven National Laboratory (BNL) and Stony Brook University (SBU) recently demonstrated two milestone experiments: the longest transmission distance (18 km) for photon entanglement over commercial fiber in the U.S. (May 2019) and the longest (~140 km) quantum communication qubit fiber link in the U.S. (July 2020). Recently, this testbed has been expanded to include atomic quantum memory operation (February 2021). We have observed Hong-Ou-Mandel (HOM) interference between indistinguishable telecom photons produced in two independent room temperature quantum memories separated by a distance of 158 km.
Classical Control Network
The BNL-SBU quantum network is controlled by a purpose-built classical data network. Each node includes a timing switch that supports the White Rabbit protocol. This system has been used to achieve nanosecond-level timing synchronization between the two campuses. Additionally, a hardware controller is used for quantum device triggering and network orchestration, and a software-defined node controller that manages and controls the operation of the nodes. Two fiber strands are used to carry all of the necessary classical signals for data, timing, and orchestration. These fibers are connected to Dense Wavelength Division Multiplexer (DWDM) systems at each end that multiplex/demultiplex several C-band channels. The DWDM systems include transponders, preamplifiers, booster amplifiers, and dispersion compensation modules that enable reliable transmission of signals over the 70 km fiber span. Additionally, Filter Wavelength Division Multiplexers (FWDMs) are used at each end to inject O-band signals into the fibers along with C-band signals. The classical side of the network has one standard switch at each location used to interconnect all quantum node control devices within a private network domain spanning both campuses. Additional attenuated laser signals in the O-band range are used to perform polarization stabilization on both quantum channels via a feedback loop that matches the polarization axes at the Quantum Information Science (QIS) creation and measurement stations.
