Padmapriya Mohan
Optics is one of the oldest disciplines pursued by humankind. The nature of light has fascinated physicists for thousands of years, and indeed, theories of light have been fundamental in our understanding of the universe. Classical photonics, a well established domain with numerous applications, exploits light as the medium for fast and reliable communication. Light, however, is inherently a quantum mechanical system; photons undergo the quantum phenomenon of superposition, interference, and entanglement. Leveraging these “strange” quantum properties of photons may allow for significant advancements in information processing in the areas of communication, metrology, sensing, and even quantum computing.
The photonic approach has several advantages over other modalities, the biggest being photons are a relatively decoherence free choice of quantum system. In fact, they barely interact, which while ideal in terms of noise, presents challenges when it comes to entangling individual photons and manipulating them. Once entangled, photons can maintain entanglement over long times and distances, which is promising for tasks in quantum communication. Another upside is the ability to operate at room temperatures; it is not necessary to cool circuit elements to cryogenic temperatures. The most basic components of a photonics based information processing system include a single-photon source, which generates photons. Information is encoded in the photon, either by virtue of how it is polarised, or its path, or in some other property of the particle. Beam splitters, polarisation filters, and phase shifters may be used to manipulate the information on the photon while it is “in-flight”. Photon loss, which is a consequence of imperfect generation and detection techniques and of the scattering and absorption in optical elements, is a fundamental limiting factor researchers are trying to address. While photons are ideal for transmission since they are “in-flight”, it might be necessary to delay or store them as part of the information processing task. To this end, optical quantum memories as well as repeaters need to be developed to ensure high fidelity and suppressed error rates. The realisation of error correction on photonic circuits is another challenge researchers are tackling, along with the development of algorithms and protocols for computation and communication.
Key players in the quantum photonics ecosystem – domestic and international
Despite these difficulties, and several more that could deter the commercialisation of the technology, things are looking good for the quantum photonics industry. Globally, both governments and companies are investing millions of dollars to achieve efficient quantum computers, quantum communication systems, key distribution systems, quantum sensors, and more using photonics.
British start-up ORCA Computing, which has recently partnered with the British Defence Ministry, is developing a modular quantum computing platform that works on photonic qubits. A key offering is its state-of-the-art quantum memory to store photons that are “in-flight”.
Canada’s Photonic Inc, which originated at Simon Fraser University, works with electrons, but uses photonic technology as interconnects and wires.
Parisian Quandela is exploiting the advancements in solid state quantum light emitters to develop solutions like a qubit generator which may be applied to applications like quantum security.
Quantum Source is an Israeli start-up that is developing a quantum processor by interlacing photons.
Based in Shanghai, TuringQ focuses on the integration of large-scale photonic circuits based on lithium niobate on insulator (LNOI) photonic chips, and the company has already released its first commercial 3D optical quantum chip, among other products.
Borealis, available over the cloud, is Xanadu’s programmable photonic quantum computer; the company recently won the financial support of the Canadian government to scale its efforts towards achieving a more robust photonic quantum computer.
PsiQuantum, a California based start-up, is one of the pioneers in the game, and was one of the early adopters of the silicon-photonic route to quantum computing.
In India, where quantum communication leads the development in quantum technologies, photonics plays a significant role. QNu Labs, one of the biggest quantum start-ups in the country, is developing photonics based QKD solutions for security.
Quanfluence is another company that is exploring photonics to achieve fault tolerant quantum computing.
QuLabs, which offers both hardware as well as software solutions based on photonic QIP, is developing optical memories and repeaters.
QpiAI recently announced the QpiAISense platform, which will soon support its AI processor which is based on silicon photonics.
Several research labs at RRI, IIT Kanpur, IIT Roorkee, IISc, NPL, and IIT Bombay among others, are focusing on advancing current photonics tech to realise robust quantum communication and key distribution systems.
Implications for the ecosystem
Photonics offers a unique advantage in that it is easy to scale. It is possible to leverage technologies that are ubiquitous in classical photonics – fabrication, optical fibre networks, and more – to scale photonic QIP hardware. Such an approach, that makes use of existing components, has far reaching and profound consequences for the classical and quantum hardware ecosystems. Integration with current classical communication networks, although a challenge, is paramount for the success of quantum photonics. Fortunately, any theoretical and experimental effort in that direction has benefits beyond quantum technology. For instance, the development of quantum dots for use as single-photon sources has led to the discovery of novel optical and electronic properties of these materials, which are relevant even beyond quantum computing and communication.
The successful adoption of quantum photonics will depend on more than just the technical robustness of the hardware. Indeed, there is a long way to go for the industry in terms of integration, standardisation, and migration. A key point of consideration is how quantum photonic solutions integrate and interface with other emerging tech – AI, 5G, blockchain, etc, as well as with current classical photonic systems. Assuming favourable ecosystem conditions achieved through national policy and collaborations across the board, one can be positive that quantum photonics holds long-term promise as an approach for technologists to pursue.
References:
- O’Brien, J., Furusawa, A. & Vučković, J. Photonic quantum technologies. Nature Photon 3, 687–695 (2009). https://doi.org/10.1038/nphoton.2009.229
- Slussarenko, Sergei & Pryde, Geoff. (2019). Photonic quantum information processing: A concise review. Applied Physics Reviews. 6. 041303. 10.1063/1.5115814.
- https://www.esa.int/Enabling_Support/Space_Engineering_Technology/Photonic_Components
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