#microringresonators

Scaler Chip

Chip-scale photonics uses photonic integrated circuits to produce, manipulate, and detect quantum states of light. These devices' high density and performance are designed to promote quantum technology by enabling quantum computing and systems outside conventional light noise. For large-scale quantum information processing, integrated photonics is the best candidate since it is compatible with complementary metal-oxide-semiconductor (CMOS) fabrication methods, which are utilised in classical communications and microprocessors.

Chip-scale integration builds tiny, dependable, portable, and deployable quantum systems by merging numerous components on one substrate.

Important aspects of chip-scale photonics include:

Platforms: Silicon photonics is a suitable platform for this integration due to its well-established semiconductor production methods, high nonlinearity, programmable routing, and affordability. Silicon nitride (Si3N4), lithium niobate, aluminium nitride, and high-index doped silica are also being developed for integrated components. Many quantum technologies use quantum light sources.

Sources of entangled photon pairs include spontaneous four-wave mixing (SFWM) in silicon waveguides and SPDC in thin-film lithium niobate. Famous for their efficiency and small size, microring resonators (MRRs) are popular. They also need less pump power. Alternative materials like Si3N4 and Hydex are being researched for high laser power due to their lower propagation loss and greater transparency.

Ideal single photon sources are on-demand, deterministic, and indistinguishable. From parametric sources, “heralded single-photon generation” detects one photon and announces the presence of another. Scholars want high spectral purity for interference-based QIP and to overcome brightness-purity trade-offs.

Squeezed light sources reduce noise below the quantum limit, improving measurement accuracy. Dual-pump SFWM in MRRs and Si3N4 MRRs are examples of integrated photonics' progress in source preparation.

Modulators (Phase Shifters): Phase shifters precisely regulate photons. Silicon phase shifters often use plasma dispersion (PD) or thermo-optic (TO) phenomena. Despite their simplicity, TO modulators are slow and cause thermal crosstalk. While PD modulators are faster, absorption losses may occur. High-speed, low-loss electro-optic modulators are being researched using hybrid integration approaches like silicon with lithium niobate or barium titanate.

Single photon detectors: High efficiency, low dark counts, and time resolution are needed. SNSPDs are desirable because of their great performance, however they need cryogenic operation. Despite their poor performance, on-chip SNSPDs and other room-temperature technologies like silicon avalanche photodiodes and transition-edge sensors are being developed. Effective coupling of PIC waveguides with detectors is important to explore.

“Chip-Scale photonics Enables Advanced Quantum Communication and Sensing Technologies” covered photonic integrated circuits (PICs) that make and detect CV quantum states of light on June 7, 2025.

Chip-scale devices can operate outside light noise, which will improve quantum technology, especially secure communication and precise sensing (e.g., gravitational wave detection). The paper was based on a review paper titled “Integrated photonics for continuous-variable quantum optics,” co-authored by Southampton, NIST, and Bristol experts.

To fulfil the demand for scalable quantum technologies, CV quantum photonic systems are being integrated onto PICs. Some highlights from the

Technology: CV quantum photonics encodes and processes quantum information using light properties like amplitude and phase, making it compatible with present telecommunications infrastructure.

Feasibility and Platforms: Investigations have shown that integrated platforms can create and modify CV states, with silicon photonics being particularly promising.

Recent developments: Integrated photonic-electronic receivers can transmit data at 10 Gbaud, and CV-QKD (Quantum Key Distribution) can be extended to 100km fibre optic lines with local oscillators to avoid discrete optical component issues.

Component Integration:

Sources: Squeezed states improve gravitational wave detection sensitivity by reducing noise below the quantum limit. The mentions spontaneous parametric down-conversion (SPDC) and other PIC electro-optic modulation approaches.

Detectors: Cryogenic but extremely efficient SNSPDs and other room-temperature detector technologies like silicon avalanche photodiodes and transition-edge sensors are covered. Effective coupling between PIC waveguides and detectors remains a research priority.

System Integration: Integrated detectors and photonic circuits on a chip enable portable and deployable systems. This integration makes quantum systems compact and trustworthy.

Challenges and Future Work: The paper emphasises the need to study non-Gaussian quantum states to increase performance and expand quantum information processing. Scalability is crucial, and modular techniques using networked chip designs can help. Future priorities will include developing more deterministic and efficient non-Gaussian states, improving detector integration (especially room-temperature detectors), and researching CV system-specific error correction protocols to improve robustness against noise and decoherence.