Quantum information science promises to revolutionize computation, communication, and sensing by exploiting quantum mechanical phenomena — superposition, entanglement, and interference — that have no classical analogue. Among the various physical platforms being developed for quantum computing and quantum communication, photonic systems hold unique advantages: photons travel at the speed of light, interact minimally with their environment (enabling long coherence times), and can be transmitted through fiber optic networks with low loss. These properties make integrated quantum photonics one of the most promising platforms for both near-term and long-term quantum information applications.
Why Photons for Quantum Computing?
Building a practical quantum computer requires qubits — quantum mechanical two-level systems — that can be prepared in arbitrary superposition states, manipulated with high-fidelity quantum gates, and measured with high efficiency. Several physical implementations are competing: superconducting qubits (pursued by Google, IBM, and Rigetti), trapped ion qubits (IonQ, Quantinuum), nitrogen-vacancy centers in diamond, and photonic qubits.
Each approach has distinct advantages and challenges. Superconducting qubits offer fast gate times and established fabrication processes but require cooling to millikelvin temperatures and are difficult to connect across distances. Photonic qubits operate at room temperature, can be transmitted over long distances through fiber networks, and can leverage the mature silicon photonics manufacturing ecosystem. The main challenge is that photons, being bosons, do not interact with each other naturally — implementing the two-qubit entangling gates needed for universal quantum computation requires either strong optical nonlinearities (which are extremely difficult to achieve at the single-photon level) or measurement-induced interaction protocols (which require high-efficiency single-photon detection and fast feed-forward control).
Linear Optical Quantum Computing
A seminal 2001 paper by Knill, Laflamme, and Milburn (KLM) proved that universal quantum computation is achievable using only linear optics — beam splitters, phase shifters, and single-photon detectors — without requiring any nonlinear optical interactions. The KLM protocol achieves two-qubit gates probabilistically, using ancilla photons and post-selection. While the original KLM scheme was resource-intensive, subsequent theoretical work has shown that these overhead requirements can be dramatically reduced using cluster state approaches and percolation arguments.
Photonic Quantum Computing (PQC) companies like PsiQuantum and Xanadu are pursuing large-scale photonic quantum computers based on these principles. PsiQuantum's approach targets fault-tolerant quantum computation based on topological codes, aiming to build a million-qubit system using silicon photonics fabricated at GlobalFoundries' advanced logic fabs. Xanadu's Borealis system uses squeezed light and Gaussian boson sampling to implement quantum advantage for specific computational tasks on hardware available today through their Strawberry Fields cloud platform.
Photons are the natural carriers of quantum information. They travel at the speed of light, don't interact with thermal noise at room temperature, and can connect quantum nodes across a continent via existing fiber optic infrastructure.
Quantum Key Distribution
While universal quantum computing with photons faces significant remaining engineering challenges, quantum key distribution (QKD) is already a mature commercial technology. QKD uses the quantum properties of individual photons to distribute cryptographic keys between two parties with information-theoretic security — any eavesdropper necessarily disturbs the photon states in detectable ways, alerting the legitimate parties to the intrusion.
Commercial QKD systems are deployed in metropolitan fiber networks in China, Japan, Europe, and the United States. China has demonstrated QKD over a 2,000-kilometer fiber backbone network and extended it to satellite links spanning over 7,000 kilometers. The primary technical challenge is extending QKD range, as photon loss in fiber limits transmission distance to a few hundred kilometers without quantum repeaters. Integrated photonic chips are enabling miniaturization of QKD transmitter and receiver modules, reducing cost and enabling deployment in space-constrained network infrastructure.
Wove Photonic's Quantum Research
Our quantum photonics research program focuses on developing integrated photonic platforms that can support both near-term QKD applications and longer-term photonic quantum computing implementations. Key research directions include:
Integrated photon pair sources: We are developing spontaneous parametric down-conversion (SPDC) and spontaneous four-wave mixing (SFWM) sources integrated in our silicon nitride platform. These sources generate pairs of quantum-entangled photons on-chip, with brightness and purity characteristics that enable high-fidelity quantum operations.
Low-loss photonic circuits: The ultra-low propagation losses of our silicon nitride platform are critical for quantum photonics, where photon loss directly degrades the fidelity of quantum states. Our sub-0.1 dB/cm propagation losses translate to less than 1% loss per 10 centimeters of waveguide — enabling complex quantum photonic circuits with many components while maintaining high photon collection efficiency.
Integrated single-photon detectors: We are collaborating with leading groups developing superconducting nanowire single-photon detectors (SNSPDs) integrated directly on our photonic chips. On-chip detection eliminates coupling losses between the photonic circuit and external detectors, dramatically improving system efficiency.
The Long View
Quantum photonics is a long-term technology development program. Near-term opportunities in QKD and quantum sensing are real and growing, but full-scale fault-tolerant photonic quantum computing remains a decade or more away. What is driving investment today is the recognition that building the integrated photonic infrastructure for quantum applications requires developing the same manufacturing capabilities needed for photonic computing and sensing — making quantum photonics research a strategic contributor to Wove Photonic's core platform development even as its direct commercial applications mature more slowly than our primary markets.