Research Roundup August 2023 - Hardware

Shown below are summaries of a few interesting research papers in quantum technology that we have seen over the past month.

High-efficiency single photon emission from a silicon T-center in a nanobeam

Organizations: University of Maryland; Simon Fraser University; Photonic Inc.

Optically active solid-state qubits are important for quantum computers, networks, and sensors. Integrating these qubits with nanophotonic devices enhances photon emission and light-matter interactions. The researchers employed a nanobeam structure that efficiently emitted light in a mode matched to a lensed single-mode fiber, allowing them to collect more than 70% of the T center’s emission. This is the highest T center count rate so far documented. The next?stride forward?will involve coupling the zero phonon line to a cavity mode to enhance the?brightness.

Link: https://arxiv.org/abs/2308.04541?

Scalable Multipartite Entanglement Created by Spin Exchange in an Optical Lattice

Organizations: University of Science and Technology of China; Fudan University; Tsinghua University

Optical superlattices are the natural system for performing parallel operations on ultracold atoms while quantum gas microscopes excel at single-atom manipulation. Here, these technologies were combined with digital micromirror devices to create and detect large-scale multipartite entanglement. This architecture allowed layers of quantum gates to be applied to atoms separated at moderate distances. The researchers successfully prepared Bell states with both a high fidelity and a long lifetime, and then extended this entanglement to more complex states involving one-dimensional chains and two-dimensional plaquettes. They verified this entanglement using rigorous criteria.

Link: https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.131.073401?

Potential Energy Advantage of Quantum Economy Organizations

The University of Chicago; qBraid ; SeQure ; University of Toronto; University of Hong Kong

This study focuses on the escalating energy demands of the modern computing sector due to the widespread use of large-scale machine learning and language models. It addresses the significance of energy conservation for computing service providers in terms of their market expansion and compliance with governmental regulations. The authors assess the possibility of quantum computing having an energy advantage over classical computing. They suggest that quantum computing might offer a more sustainable trajectory for the computing industry but only when quantum computing is deployed at sufficient scale. Using real-world physical parameters, they quantify the operational scale required to achieve this energy-efficient edge.

Link: https://arxiv.org/abs/2308.08025

Modular Superconducting Qubit Architecture with a Multi-chip Tunable Coupler

Organization: Rigetti Computing

The paper describes three different designs of multi-chip tunable couplers using vacuum gap capacitors or superconducting indium bump bonds to create a floating tunable coupler which mediate interactions between qubits on separate chips to build a modular architecture. The paper also shows that two-qubit gate operations between chips can have a fidelity at the same level as qubits with a tunable coupler on a single chip. Such a technology could be important for creating a modular and scalable quantum computer.

Link: https://arxiv.org/abs/2308.09240

Constant-Overhead Fault-Tolerant Quantum Computation with Reconfigurable Atom Arrays Organizations

The University of Chicago; Harvard University; California Institute of Technology; University of Arizona; QuEra Computing Inc.

This preprint proposes a practical method for fault-tolerant quantum computation using quantum low-density parity-check (qLDPC) codes on reconfigurable atom arrays. These codes offer high encoding rates but have experimentally challenging long-range connectivity requirements. The team devised an efficient approach that capitalizes on the product structure of qLDPC codes by using atom rearrangement to enable non-local syndrome extraction. They verified the fault tolerance of their protocols, conducted simulations of memory and logical operations, and found that their qLDPC-based setup outperforms the surface code in terms of qubit requirements. This opens the door to practical, low-overhead quantum computing using qLDPC codes and existing experimental techniques.

Link: https://arxiv.org/abs/2308.08648?

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