China achieves new progress in photonic quantum chip research

Photonic quantum chip is widely seen as a key pathway toward the practical deployment of optical quantum information technologies. Today’s mainstream photonic quantum chips typically rely on probabilistic single-photon sources generated through nonlinear optical processes, but the certain probability property of photons will lead to low emission efficiency and make the preparation of multi-photon qubits extremely challenging.

In contrast, solid-state atoms feature atom-like two-level structures that enable deterministic, highly efficient single-photon emission—an ideal foundation for on-chip multi-photon qubit generation. However, solid-state quantum emitters face major hurdles, including inhomogeneous spectral broadening and the lack of efficient hybrid-integration techniques, constraining their potential in large-scale on-chip integration and quantum networking.

To address these challenges, researchers from the Shanghai Institute of Microsystem and Information Technology (SIMIT), Chinese Academy of Sciences, together with Sun Yat-sen University and the University of Science and Technology of China, have developed a hybrid-integrated photonic quantum chip combining deterministic solid-state atomic single-photon sources (semiconductor quantum dots) with low-loss lithium niobate thin films. They introduced a new on-chip localized stress-engineering method enabled by ferroelectric-domain engineering in lithium niobate thin films, achieving wide-range, high-dynamic, and reversible fine-tuning of quantum-dot emission spectra.

The team also advanced a high-precision “micro-transfer-printing” hybrid integration approach with nanometer-scale accuracy, enabling synchronous on-chip integration and spectral tuning of up to 20 deterministic quantum-dot single-photon sources. Building on innovations in material functionality and hybrid chip architecture, the researchers demonstrated on-chip quantum interference between spatially separated quantum-dot single-photon emitters—an important milestone toward scalable on-chip quantum networks.

By combining self-assembled quantum dots with lithium niobate—two quantum materials with strong advantages in optical research—the team tackled the long-standing challenge of scalable multi-photon state generation. Their micro-transfer-printing process enabled the integration of 20 deterministic quantum emitters on a low-loss lithium niobate photonic chip, building the largest hybrid-integrated photonic quantum chip based on quantum-dot deterministic single-photon sources reported to date.

To overcome inherent inhomogeneous spectral broadening in solid-state emitters such as quantum dots and diamond color centers, the team introduced a DC-voltage-driven localized stress-tuning technique based on ferroelectric-domain engineering in lithium niobate thin films. This method integrates five critical capabilities: on-chip compatibility, wide-range tunability, operation at cryogenic (4 K) temperatures, ultra-low power consumption (at the milliwatt level), and full reversibility. Beyond expanding lithium niobate’s traditional roles in electro-optic modulation and surface acoustic waves, this approach opens a new avenue for on-chip quantum control and provides technical guidance for emerging ferroelectric thin films, including barium titanate and strontium titanate.

By bridging two quantum materials—self-assembled quantum dots and lithium niobate—this work establishes a new technological route for scaling photonic quantum chips. The demonstrated integration density reaches 67 quantum emitters per mm, enabling centimeter-scale chips to host more than 1,000 quantum channels.

Each channel’s localized stress control requires only microwatt-level power, representing a three-order-of-magnitude reduction compared with milliwatt-level thermo-optic tuning in silicon photonics. Its cryogenic compatibility and ultra-low power demand also allow seamless integration with superconducting nanowire single-photon detectors.

Looking ahead, the team plans to harness lithium niobate’s high-speed electro-optic properties to realize fast on-chip photon routing and entanglement distribution—paving the way toward fault-tolerant linear optical quantum computing and scalable quantum internet architectures.

Source: TrendForce, Taiwan.