Center for Quantum Networks (CQN)

The Center for Quantum Networks (CQN) is an Engineering Research Center (ERC) aiming to develop the entire technology stack to upgrade the internet to reliably carry quantum data across the globe, serving diverse applications across many concurrent user groups. CQN, the first ERC in a quantum-technology topic, was founded by Prof. Saikat Guha as PI/Director in 2020 when he was at the University of Arizona, along with a highly-interdisciplinary yet closely-integrated team involving 20+ faculty across 10 university campuses. CQN, now a community of roughly 150 people (students, postdocs, faculty and administrators) and remains head-quartered at the Unviersity of Arizona (with Prof. Matt Eichenfield at UArizona now as co-Director alongwith Prof. Guha at UMD, Prof. Dirk Englund at MIT serving as Deputy Director, and Ms. Julie Emms as Administrative Director). Core partner universities include MIT (PI: Prof. Dirk Englund), UMD (PI: Prof. Saikat Guha), UMass Amherst (PI: Prof. Don Towsley) and Harvard University (PI: Prof. Marko Loncar).

CQN’s research spans the entire technology stack—theory and experiments included—underlying quantum networking. At the highest level, CQN aspires to build the first viable and scalable quantum repeater, a technology that will enable long-range high-speed transport of quantum data packets, and the entire network protocol stack from the physical layer to the application layer, to support future-compatible scalable quantum networking whose use cases will have widespread societal impact. CQN’s research includes:

• [Thrust 3] Novel spin-based memories (e.g., molecular qubit memories being developed by Prof. Danna Freedman at MIT),
• [Thrust 3 -> Thrust 2] Scalable fabrication of color centers qubits in diamond (Prof. Englund, MIT; Prof. Matt Eichenfield, UArizona), and associated design of photonic cavities (Prof. Marko Loncar, Harvard; Prof. Ryan Camacho, BYU), strain tuning of the emission wavelengths (Prof. Eichenfield), nuclear-spin-mediated quantum logic gates (Prof. Mikhail Lukin, Harvard), quantum frequency conversion (Prof. Loncar, Englund, Prof. Julia Mundy, Harvard, and Prof. Brian Smith of University of Oregon), scalable cryo-electronic digital processing within the repeater (Prof. Karl Berggren, MIT), and diamond annealing (Prof. Tina Brower Thomas, Howard University),
• [Thrust 2] The zero-added-loss-multimplexing (ZALM) source as a mediator of high-bandwidth entanglement generation across a network link; analysis and design: Prof. Mike Raymer, U. Oregon, Prof. Jeff Shapiro, MIT; Experimental build including frequency and temporal mode conversion: Prof. Brian Smith, U. Oregon and Dr. Franco Wong, MIT.
• [Thrust 2] Error correction and entanglement distillation at the link level and at the network level (Profs. Narayanan Rengaswamy and Bane Vasic, UArizona, Prof. Stefan Krastanov, UMass Amherst; Prof. Saikat Guha, UMD).
• [Thrust 2 -> Thrust 1] Quantum repeater architecture and analysis (Prof. Liang Jiang, U. Chicago, Prof. Guha, UMD, Prof. Filip Rozpedek, UMass Amherst, Prof. Don Towsley, UMass Amherst), and
• [Thrust 1] Quantum networking: network architectures, algorithms and protocols for routing, scheduling, tomography (Prof. Don Towsley, UMass Amherst, Prof. Ines Montano, NAU, Prof. Saikat Guha, UMD, Prof. Gayane Vardoyan, UMass Amherst)

CQN has multiple testbeds: (1) the Boston area testbed (also known as BARQNET) led by Prof. Dirk Englund, which connects MIT Lincoln Laboratory with MIT campus, to Harvard, over to BBN Technologies, with connections to Boston University campus, where a CQN spinout company Qunett resides. This testbed has led several ``world’s first” demonstrations in metropolitan-area quantum communications experiments. (2) the Tucson area testbed (also known as QUCSON) led by Prof. Matt Eichenfield, which is a campus-wide testbed at UArizona campus connecting 10 laboratory sites across 6 buildings, equipped with SiV and SnV memory modules, frequency conversion to telecom, switches, modulators and WDM telecom equipment, and superconducting nanowire detectors. In addition to serving as the proving ground for vertical integration of devices and components, QUCSON has proven an attractive means of industry engagement. (3) CQN is expanding into hybrid networking connecting SiV color centers with trapped ion qubits, to bring in robust quantum-logic capability, which is being developed as part of the UMD-campus MARQI network, led by Edo Waks. Funded by NSF’s Convergence Accelerator program, the MARQI network is connected to the DMV area DC-QNET network infrastructure, home to many government, academic and industry stakeholders, as well as quantum networking programs and demonstrations. (4) Finally, led by Prof. Stefan Krastanov of UMass Amherst, CQN is developing a full-stack Virtual Testbed—a digital twin of CQN’s quantum network architecture replete with all physical and matheamtical details spanning quantum memory physics to spin photon interfaces to entanglement distillation to network theory to applications. This Virtual Testbed, in addition to serving as a design, evaluation and research tool, has also proven a source of technical integration across the wide swath of disciplines that CQN brings together.

CQN’s innovation ecosystem led by Dr. Alireza Shabani—comprising of the QED-C and 20+ industry members participating at various partnership levels in varying technical capacities, aspires to spur new technology industries and a competitive marketplace of quantum service providers and application developers some day. CQN’s Education and Workforce Development (EWD) program, led by Dr. Noel Hennessey, engages the entire spectrum of US students spanning K-12, undergraduate students, graduate students, and post-graduate practioners in the field. CQN’s Diversity and Culture of Inclusion (DCI) program, led by Dr. Julie Des Jardins, is a unique initiative aimed at creating a program execution framework and way-of-life across the entire center to inculcate a culture of inclusion that can become a role model for STEM Science and Engineering research centers across the country.