Quantum Information Processing with Photonic Systems

Quantum information processing with photonic systems harnesses the quantum properties of light to encode, transmit and manipulate information. Photons, as carriers of quantum bits, offer low decoherence and intrinsic compatibility with optical networks, making them ideal for long-distance quantum communication and scalable computing architectures. Central to these endeavours are multiphoton entangled states—such as cluster states and Greenberger–Horne–Zeilinger (GHZ) states—which underpin measurement-based models of quantum computation and all-photonic repeater schemes. Semiconductor quantum dots and atom–cavity systems have emerged as versatile sources of on-demand indistinguishable photons, enabling deterministic generation of entangled strings at gigahertz rates. Measurement-based approaches leverage pre-prepared entangled resource states, upon which adaptive single-photon measurements and feedforward control implement logical operations while tolerating photon loss. Fault-tolerant architectures exploit fusion operations—entangling measurements that probabilistically link smaller entangled blocks into large-scale graph states—thereby circumventing the need for strong optical nonlinearities. Recent advances in integrated photonic circuits, high-efficiency detectors and error-correcting codes for loss tolerance have collectively driven the field towards practical implementations of quantum networks, secure communication protocols and photonic quantum processors.

Research from Nature Portfolio

Recent studies have demonstrated deterministic on-chip production of long strings of indistinguishable photons in cluster states at gigahertz repetition rates using semiconductor quantum dots interfaced with photonic cavities. These developments achieved entanglement lengths of around ten photons, paving the way for scalable measurement-based quantum computers and all-photonic repeaters. Another key advance introduced a fusion-based quantum computation model tailored for photonic systems. In this scheme, small entangled resource states are linked by entangling measurements called fusions, enabling a modular, fault-tolerant architecture that tolerates significant photon loss per fusion and reduces classical processing overhead. These works illustrate a shift towards resource-efficient, deterministic photonic schemes capable of meeting the thresholds required for practical fault tolerance.

Quantum Information Processing with Photonic Systems publication trend

The graph below shows the total number of articles in quantum information processing with photonic systems across all publications each year (not limited to Nature Index journals).

Technical terms

Entanglement: A quantum correlation between particles such that the state of each cannot be described independently of the others, enabling nonclassical information processing.

Cluster state: A highly entangled multiqubit graph state organised on a lattice, serving as a universal resource for measurement-based quantum computation.

Fusion: A probabilistic entangling measurement that merges smaller photonic resource states into larger graph or cluster states without requiring deterministic two-photon gates.

Graph code: A quantum error-correcting code represented by a graph, where vertices correspond to qubits and edges define entangling relationships, designed to protect against qubit loss and operational errors.

References

1. Deterministic generation of indistinguishable photons in a cluster state. Nature Photonics (2023).
2. Continuous and deterministic all-photonic cluster state of indistinguishable photons. Reports on Progress in Physics (2024).
3. Fusion-based quantum computation. Nature Communications (2023).
4. Optimizing Graph Codes for Measurement-Based Loss Tolerance. PRX Quantum (2023).
5. High-fidelity four-photon GHZ states on chip. npj Quantum Information (2024).