The mission of the NSF Quantum Leap Challenge Institute for Hybrid Quantum Architectures and Networks (HQAN) is to tackle the challenge of scaling quantum processors by pursuing an alternative paradigm: distributed quantum processing and networks composed of a hybrid architecture. This modular approach leverages the strengths of different quantum systems and has the potential to unlock quantum information processing at large scales. New distributed applications enabled by this approach may include unconditionally secure information searching and multi-party computation.

HQAN personnel will carry out fundamental science research and engineering to develop a multi-node, full-stack system, ranging from quantum processor design and control to a high-level software application interface. A convergent approach will be pursued by bringing together researchers with expertise from chemistry, computer science, electrical and computer engineering, mathematics, materials science and engineering, molecular engineering, and physics.

HQAN Research Projects

A key challenge to advancing quantum information science and engineering is developing the hardware needed to realize distributed processors and networks based on hybrid architectures. To meet this challenge, HQAN researchers will create multi-node distributed quantum processors and network testbeds at each of the principal sites. Proven technologies—superconducting circuits, trapped atomic ions, and neutral atoms—with sufficient logic gate fidelity to achieve new applications will be employed. HQAN will extend existing techniques and develop new methods to scale up to multiply connected networks composed of at least three nodes, each consisting of several qubits. Initially, each testbed will be based on a single architecture that will be used to benchmark new network protocols and algorithms. In parallel, interconnect technologies capable of linking different hardware platforms will be developed. These technologies will be shared between HQAN institutions, thereby enabling the second generation of network testbeds that are composed of hybrid systems with enhanced functionality.  

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Achieving practical distributed quantum computing and networking that leverages hybrid architectures requires new approaches to protocols and software. To tackle this problem, HQAN researchers employ a software toolchain development approach that is concurrent with hardware advancements. This convergent HQAN approach is interdisciplinary—computer science, electrical and computer engineering, mathematics, and physics theory and software researchers will be co-located and embedded with engineers and experimenters at the HQAN testbeds. HQAN researchers will target identifying methods for validating and optimizing distributed, hybrid processors and developing new applications and protocols that take advantage of this architecture. Close-knit interactions with the HQAN partners will leverage key ideas and lessons learned from pioneering activities such as Google Circ, IBM Qiskit, and the IBM Q Experience.

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Error correction is necessary to achieving high performance in any quantum computing approach, including distributed schemes. The standard error correction strategy involves tremendous overhead in physical qubits and logic gate depth. HQAN researchers will pursue an alternative technique that is less demanding: topologically protected qubits. Three approaches will be pursued in parallel—Majorana bound states in superconducting Josephson junctions, proximitized holes in strained germanium, and π-periodic superconducting metamaterials. The common challenges in these systems will be overcome by leveraging interdisciplinary and inter-institutional teams. HQAN researchers will work towards advancing these nascent technologies to functionality and integration into the HQAN superconducting network testbeds.

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