[Paper Review] Minimizing resource overhead in fusion-based quantum computation using hybrid spin-photon devices

Stephen C. Wein, Timothée Goubault de Brugière+4 more|arXiv (Cornell University)|Dec 11, 2024

Quantum Information and Cryptography4 citations

TL;DR

This paper proposes a hybrid spin-photon architecture using deterministic single-photon sources with embedded matter qubits to minimize resource overhead in fusion-based quantum computing. By employing repeat-until-success (RUS) entangling gates, the scheme achieves near-deterministic generation of a 24-photon (2,2)-Shor-encoded 6-ring resource state with orders-of-magnitude lower hardware requirements than probabilistic alternatives, significantly reducing loss and enabling fault-tolerant photonic quantum computation.

ABSTRACT

We present three schemes for constructing a (2,2)-Shor-encoded 6-ring photonic resource state for fusion-based quantum computing, each relying on a different type of photon source. We benchmark these architectures by analyzing their ability to achieve the loss tolerance threshold for fusion-based quantum computation using the target resource state. More precisely, we estimate their minimum hardware requirements for fault-tolerant quantum computation in terms of the number of photon sources to achieve on-demand generation of resource states with a desired generation period. Notably, we find that a group of 12 deterministic single-photon sources containing a single matter qubit degree of freedom can produce the target resource state near-deterministically by exploiting entangling gates that are repeated until success. The approach is fully modular, eliminates the need for lossy large-scale multiplexing, and reduces the overhead for resource-state generation by several orders of magnitude compared to architectures using heralded single-photon sources and probabilistic linear-optical entangling gates. Our work shows that the use of deterministic single-photon sources embedding a qubit substantially shortens the path toward fault-tolerant photonic quantum computation.

Motivation & Objective

• To reduce the resource overhead in fusion-based quantum computation (FBQC), which remains a major barrier to scalable fault-tolerant photonic quantum computing.
• To address the challenge of high resource costs associated with probabilistic photon sources and linear-optical gates in generating complex graph states.
• To explore architectures that achieve high loss tolerance (7.5%) while minimizing the number of photon sources and hardware components.
• To demonstrate that deterministic single-photon sources with matter qubit degrees of freedom can drastically reduce the required hardware scale for fault-tolerant resource state generation.

Proposed method

• Designing three distinct RSG architectures: (1) all-photonic using heralded or deterministic single-photon sources, (2) using deterministic caterpillar graph state sources, and (3) using a group of deterministic sources entangled via repeat-until-success (RUS) CZ gates.
• Employing RUS entangling gates to achieve near-deterministic entanglement between photonic qubits, leveraging high-fidelity, high-indistinguishability single photons from quantum dots in micropillar cavities.
• Utilizing modular, scalable design principles that avoid large-scale multiplexing and reduce loss by eliminating probabilistic post-selection steps.
• Benchmarking architectures based on minimum hardware requirements—specifically, the number of photon sources needed to achieve a desired resource state generation period.
• Modeling and simulating the performance of each architecture under realistic constraints, including photon indistinguishability, fidelity, and component losses.
• Focusing on the (2,2)-Shor-encoded 6-ring graph state, which enables a 7.5% loss tolerance threshold when used with biased measurements.

Experimental results

Research questions

• RQ1 Can deterministic single-photon sources with embedded matter qubits significantly reduce the resource overhead in generating complex photonic resource states for fusion-based quantum computing?
• RQ2 How does the use of repeat-until-success (RUS) entangling gates compare to probabilistic linear-optical gates in terms of hardware efficiency and loss tolerance?
• RQ3 What is the minimum number of photon sources required to achieve near-deterministic generation of a 24-photon (2,2)-Shor-encoded 6-ring resource state?
• RQ4 To what extent can modular, deterministic architectures eliminate the need for lossy large-scale multiplexing in photonic quantum computing?
• RQ5 Can hybrid spin-photon devices enable fault-tolerant quantum computation with orders-of-magnitude lower hardware requirements than current probabilistic approaches?

Key findings

• A group of 12 deterministic single-photon sources, each with a single matter qubit degree of freedom, can generate the target (2,2)-Shor-encoded 6-ring resource state near-deterministically using repeated RUS CZ gates.
• The proposed RUS-based architecture reduces resource overhead by several orders of magnitude compared to architectures using heralded single-photon sources and probabilistic linear-optical entangling gates.
• The scheme achieves near-deterministic resource state generation without requiring large-scale multiplexing, thereby minimizing photon loss and improving scalability.
• The approach is fully modular and reconfigurable, allowing for easy replacement of defective components and dynamic reconfiguration for different quantum tasks.
• With current state-of-the-art photon indistinguishability (>99.5%) and fidelity (>99.3% for single-qubit gates), the method enables a 24-photon resource state with fidelity exceeding 99.95%.
• The architecture supports fault-tolerant quantum computation with a 7.5% loss tolerance threshold when combined with biased measurements, meeting the best-known threshold for FBQC.