We evaluate the utility of the spin-zero manifold of an exchange-coupled array of $N$ spins for tasks in quantum computation and quantum simulation. Since pairs of electrons can be readily initialized into a product state of singlets in semiconducting quantum dot arrays, the full spin-zero manifold is available with exchange-only control, providing a Hilbert space of approximate dimension $2^N/(N/2)^{3/2}$ , asymptotically close to the $2^N$ dimension of the full spin Hilbert space. Leveraging the spin-zero manifold enables larger computational space in a given array compared to traditional exchange-only control, in which spin arrays are organized into modular units of $n$ spins comprising $N/n$ encoded qubits, limiting to the exponentially smaller Hilbert dimension $2^{N/n}$ . Here we focus on benchmarking metrics for this resource utilization by generalizing cross-entropy benchmarking, mirror benchmarking, and out-of-time-ordered correlators to this system. We show that operating in the spin-zero manifold can accelerate the realization of computational quantum advantage applications in semiconductor-based spin qubits.We evaluate the utility of the spin-zero manifold of an exchange-coupled array of $N$ spins for tasks in quantum computation and quantum simulation. Since pairs of electrons can be readily initialized into a product state of singlets in semiconducting quantum dot arrays, the full spin-zero manifold is available with exchange-only control, providing a Hilbert space of approximate dimension $2^N/(N/2)^{3/2}$, asymptotically close to the $2^N$ dimension of the full spin Hilbert space. Leveraging the spin-zero manifold enables larger computational space in a given array compared to traditional exchange-only control, in which spin arrays are organized into modular units of $n$ spins comprising $N/n$ encoded qubits, limiting to the exponentially smaller Hilbert dimension $2^{N/n}$. Here we focus on benchmarking metrics for this resource utilization by generalizing cross-entropy benchmarking, mirror benchmarking, and out-of-time-ordered correlators to this system. We show that operating in the spin-zero manifold can accelerate the realization of computational quantum advantage applications in semiconductor-based spin qubits.

quant-pharXiv:2607.06672Jul 9, 20260 citations

Benchmarking quantum computers

Timothy J Proctor, Kevin C Young, Andrew Baczewski +1 more

arXiv:2407.08828Nature Reviews PhysicsJan 7, 202571 citations

Benchmarking exchange-only control of a 48-spin singlet manifold

HRL Quantum Team, Microsoft Collaborators, : +125 more

Exchange-only quantum computing benefits from high fidelity and straightforward control afforded by the exchange interaction. However, independently controllable qubits must be encoded into subsystems of at least three electron spins, restricting computation to only a fraction of the available spin Hilbert space. The remaining states are treated as leakage and used only transiently in gate sequences. By contrast, a quantitative, system-wide measure of exchange-only performance can exploit the full available Hilbert space, including states conventionally treated as leakage. Here, we apply this approach to arrays of up to 48 electron spins, accessing a total-spin-zero Hilbert space with dimension exceeding $2^{40}$ . Measurements of out-of-time-order correlators (OTOCs) reveal rich scrambling dynamics and demonstrate access to regimes relevant to quantum computational advantage. Using generalized forms of cross-entropy and mirror randomized benchmarking, we also assess the aggregate performance of the full exchange-only system per fundamental two-body interaction: the two-spin exchange. We obtain an effective system-level error of $3 \times 10^{-4}$ per exchange, incorporating the complete experimental control sequence and all associated noise sources. This value is up to an order of magnitude lower than those reported from comparable benchmarks on other platforms at the time of writing.Exchange-only quantum computing benefits from high fidelity and straightforward control afforded by the exchange interaction. However, independently controllable qubits must be encoded into subsystems of at least three electron spins, restricting computation to only a fraction of the available spin Hilbert space. The remaining states are treated as leakage and used only transiently in gate sequences. By contrast, a quantitative, system-wide measure of exchange-only performance can exploit the full available Hilbert space, including states conventionally treated as leakage. Here, we apply this approach to arrays of up to 48 electron spins, accessing a total-spin-zero Hilbert space with dimension exceeding $2^{40}$. Measurements of out-of-time-order correlators (OTOCs) reveal rich scrambling dynamics and demonstrate access to regimes relevant to quantum computational advantage. Using generalized forms of cross-entropy and mirror randomized benchmarking, we also assess the aggregate performance of the full exchange-only system per fundamental two-body interaction: the two-spin exchange. We obtain an effective system-level error of $3 \times 10^{-4}$ per exchange, incorporating the complete experimental control sequence and all associated noise sources. This value is up to an order of magnitude lower than those reported from comparable benchmarks on other platforms at the time of writing.

quant-pharXiv:2610.07393Oct 7, 20260 citations

Benchmarking Quantum Computers

Robson Giles

Jan 1, 20240 citations

Non-Spin State Quantum Computation: A Benchmarking Experimental Scheme

Jincheng Zhang

This paper presents a novel experimental scheme for quantum computation utilizing non-spin states, specifically electronic orbital states, as quantum bits (qubits). The core claim is that leveraging non-spin states offers a pathway to simplify qubit fabrication and manipulation, ultimately enhancing the scalability of quantum computing. This scheme focuses on establishing a benchmarking experimental framework to validate the computational capabilities of such a system. The proposed methodology avoids the complexities often associated with controlling and maintaining the delicate quantum states of spins. Instead, it proposes utilizing precisely controlled electronic orbital states, offering a potentially more manageable system for early-stage quantum computation. The presented framework includes a detailed description of the experimental setup, the quantum gates being implemented, and the methods for verifying the computational outcomes. The potential impact of this approach on the future of quantum computing is discussed, emphasizing the shift towards more accessible and scalable quantum technologies.This paper presents a novel experimental scheme for quantum computation utilizing non-spin states, specifically electronic orbital states, as quantum bits (qubits). The core claim is that leveraging non-spin states offers a pathway to simplify qubit fabrication and manipulation, ultimately enhancing the scalability of quantum computing. This scheme focuses on establishing a benchmarking experimental framework to validate the computational capabilities of such a system. The proposed methodology avoids the complexities often associated with controlling and maintaining the delicate quantum states of spins. Instead, it proposes utilizing precisely controlled electronic orbital states, offering a potentially more manageable system for early-stage quantum computation. The presented framework includes a detailed description of the experimental setup, the quantum gates being implemented, and the methods for verifying the computational outcomes. The potential impact of this approach on the future of quantum computing is discussed, emphasizing the shift towards more accessible and scalable quantum technologies.

Sep 3, 20260 citations

MODELING AND IMPLEMENTATION OF SPIN-BASED QUANTUM COMPUTATION

M. E. Hawley, Geoff W. Brown, G. P. Berman

Selected topics in electornics and systemsApr 1, 20080 citations

We evaluate the utility of the spin-zero manifold of an exchange-coupled array of

N

spins for tasks in quantum computation and quantum simulation. Since pairs of electrons can be readily initialized into a product state of singlets in semiconducting quantum dot arrays, the full spin-zero manifold is available with exchange-only control, providing a Hilbert space of approximate dimension

2^N/(N/2)^{3/2}

, asymptotically close to the

2^N

dimension of the full spin Hilbert space. Leveraging the spin-zero manifold enables larger computational space in a given array compared to traditional exchange-only control, in which spin arrays are organized into modular units of

n

spins comprising

N/n

encoded qubits, limiting to the exponentially smaller Hilbert dimension

2^{N/n}

. Here we focus on benchmarking metrics for this resource utilization by generalizing cross-entropy benchmarking, mirror benchmarking, and out-of-time-ordered correlators to this system. We show that operating in the spin-zero manifold can accelerate the realization of computational quantum advantage applications in semiconductor-based spin qubits.

2^{40}

. Measurements of out-of-time-order correlators (OTOCs) reveal rich scrambling dynamics and demonstrate access to regimes relevant to quantum computational advantage. Using generalized forms of cross-entropy and mirror randomized benchmarking, we also assess the aggregate performance of the full exchange-only system per fundamental two-body interaction: the two-spin exchange. We obtain an effective system-level error of

3 \times 10^{-4}

per exchange, incorporating the complete experimental control sequence and all associated noise sources. This value is up to an order of magnitude lower than those reported from comparable benchmarks on other platforms at the time of writing.