MA1: Distributed Processor and Network Testbeds

Major Activity 1: Distributed Processor and Network Testbeds  

Research Leads: Hannes Bernien (University of Chicago) & Mark Saffman (University of Wisconsin-Madison)  
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.   

Project Descriptions

Neutral atom array distributed processor and network: Fang, Goldsmith, Kats Project Contact: Saffman  

The goal of this project is to demonstrate a three-node network composed of neutral atom quantum processors and photonic links. Atom-photon entanglement at each node will be based on integration of an array of atomic qubits constructed with optical resonators. Entanglement between nodes will be based on intermediate Bell state measurements for entanglement swapping and/or direct mapping of photons into qubit memories.  


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Image Credit: Saffman Lab


Superconducting qubit distributed processor and network: Bezryadin, Clerk, Hughes, McDermott, Schuster, Van Harlingen, Eckstein Project Contact: Pfaff & Cleland 

Superconducting testbeds will be built at the University of Chicago and University of Illinois Urbana-Champaign. The Cleland group at the University of Chicago is building superconducting quantum networks to serve as a testbed for quantum communication protocols, leveraging the high fidelity and excellent control afforded by superconducting qubits. The Pfaff group, together with the other quantum circuit labs at the University of Illinois Urbana-Champaign, is working on realizing modular quantum networks from circuit QED building blocks. Flexible and error-protected generation of remote entanglement will be explored within the IQUIST testbed facility.  


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Image Credit: Youpeng Zhong (Cleland Lab) 

Trapped atomic ion distributed processor and network: Fang, Gadway, Goldschmidt, Kats, Kwiat, Lorenz  Project Contact: DeMarco

A trapped ion network and distributed processor will be developed by HQAN researchers and deployed in the Illinois Quantum Information Science and Technology center (IQUIST) testbed facility. 88Sr+ ions will be employed as logic and memory qubits, and entanglement will be probabilistically generated by interfering photons emitted by separate ions. Two and three-node systems with several qubits per node will be created using surface trap technology with integrated photonics developed in collaboration with MIT Lincoln Laboratory. 


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Image Credit: DeMarco Lab,  L. Brian Stauffer

Interfacing superconducting qubits with atoms and photons: Goldsmith, Hughes, McDermott, Schuster Project Contacts:  SaffmanSimon  

The goal of this project is to entangle a superconducting resonator circuit with an atomic hyperfine qubit. Coupling is mediated by trapping an atom close to the superconducting resonator and a microwave excitation driving a transition between atomic Rydberg states. Saffman at UW and Simon and Schuster at UC are pursuing complementary approaches based on 2D and 3D geometries and in different frequency domains. Since atomic qubits can inter-convert readily with optical photons. the successful realization of a hybrid interface between optical and microwave domains will open the door to scalable distributed QIP schemes that rely on localized processor nodes linked by “flying” photonic qubits. 

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Image Credit: (Simon Lab)

Hybrid atom–rare earth ion memory node: Goldschmidt, High, Zhong Project Contact: Bernien

The goal of this joint effort is to develop a hybrid quantum network node consisting of a multi-mode rare earth memory and a single trapped atomic qubit Such a node could combine many desirable properties, including long memory times, multiple memory modes, telecom  operation, and processing capabilities. 


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Image Credit: (Bernien Lab)

Atom array–light interface: Bernien, Chin, Walker, Yavuz  Project Contact:  Saffman

The goal of this project is to study collective aspects of atom-light interactions. This will include sub- and super-radiant phenomena in disordered atomic ensembles as well as using periodic  arrays to engineer enhanced interaction strength. Such a periodic structure can have a wide range of applications, for instance, as a high-fidelity quantum memory or as nearly perfect mirrors consisting of only a single layer of atoms. HQAN researchers will investigate how to harness this paradigm to realize light–matter interfaces and interconnections in 1D and 2D. 


Image Credit: (Bernien Lab)

Novel solid-state quantum metasurfaces: Brar, Choy, High, Kawasaki, Yu  Project Contact: Kolkowitz 

The ultimate goal of this effort is the realization of solid-state quantum metamaterials with the capability to deterministically generate, steer, and store nonclassical states of light for use in quantum network interconnects. The experimental approach centers around a combined  scanning tunneling microscopy (STM)-fluorescence characterization platform. This methodology allows for nm-scale optical resolution, which can be directly correlated with structural features in the sample measured with the STM tip.  These capabilities will be utilized to determine the atomistic nature of optically active quantum defects in 2D materials and to controllably introduce optical defect arrays in materials with sub-nm positioning accuracy. HQAN researchers are combining this one-of-a-kind characterization tool with local defect implantation, precision epitaxial growth and doping of ultra-pure 2D materials, and theory of interacting photonic systems in a development feedback loop. These engineered defect arrays will be used to realize novel collective optical emission, absorption, and scattering properties. 



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Image Credit: (Kolkowitz Lab, Victor Brar Lab )