QUANTUM PHOTONICS


and Enabling Technologies at Innovate UK, says quantum technologies are usually divided into four main types or categories: quantum computing – using qubits to perform complex calculation or algorithms that cannot be run on classical computers – and simulation; quantum communication, which exploits the properties of photons for safe communication through quantum key distribution; quantum sensing and metrology, gravimetry and atomic clocks; and finally quantum imaging – based on the use of single photons, for example for enhanced imaging through clouded media and light spectroscopy. An Innovate UK report published in December last year identified single-photon sources as crucial to the development of quantum technology. ‘Quantum light is central to the development of secure communications and more powerful computing, powered by quantum’ it says. Quantum technologies use


a broad range of optics and photonics that can assist the manipulation, generation or detection of light states. For example, lasers play an essential part in quantum development for manipulating quantum states, and also for exciting matter at an atomic scale to generate photons. “There are other essential optical components in quantum set-ups, such as optical filters – high-reflectance low- loss mirrors, anti-reflective coatings, beam splitters and modulators. Fibre optics is also a crucial discipline for quantum-level investigation of the transmission of photons over long distances, specifically for telecommunications applications,” says Sidqi. “Recently, photonic integrated


circuits (PICs) have also been closely linked to quantum technologies – and consist of integrating quantum devices on integrated circuits to ensure compact, scalable and user- friendly products,” she adds. According to Sidqi, quantum


technologies have a broad range of industrial applications


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“There are other essential optical components in quantum set-ups, such as optical filters – high reflectance low- loss mirrors, anti- reflective coatings, beam splitters and modulators. Fibre optics is also a crucial discipline”


in areas such as industrial optimisation using quantum algorithms and computing, as well as in healthcare where they can be used for “the acceleration of material and drug discovery, brain imaging, early-stage diagnosis of tumours and cancer and disease prediction by understanding protein folding”. “Quantum technologies


also have applications in telecommunications and cybersecurity using QKD protocols, in transport, through the use of lidar, traffic management, greenhouse- gas sensing and underground imaging, in civil and military engineering through underground imaging and assets detection, seeing through clouded media and corners for defence applications, as well as in data science, precise timing – using atomic clocks – and GPS- free navigation,” she says.


The role of photonics in quantum technology One photonics company active in the quantum technologies field is California-based Nexus Photonics, which provides application- and customer-specific PICs that are specifically tailored for quantum applications. As Tin Komljenovic, Co-Founder and CEO at the company, explains, these PICs are used to provide operation in broadband wavelength range from ultraviolet (UV) to infrared (IR) with on-chip sources – and many of the quantum applications “require operation outside traditional datacom/ telecom wavelength ranges that


have historically primarily been served with PICs”. “Furthermore, our platform


enables extremely low-noise – or quiet – lasers and very low on-chip and chip-to- fibre losses due to the use of high-performance waveguides – typically based on silicon nitride – which are key for many applications as noise from the laser can impact your quantum system performance – and, in many quantum cases, you are not allowed to lose even a single photon,” he says. “Finally, as PICs enable a


high level of integration and mass manufacturing, we see them as crucial pieces to enable scaling of quantum systems, both in terms of complexity – for example, the number of qubits – as well as commercial offerings, by lowering cost to enable wider deployment.” According to Komljenovic,


many of today’s advanced quantum systems, either in sensing, computing, or networking, utilise a range of laboratory-based equipment, and moving to integrated components and PICs “will be key to taking them out of the lab”. In his view, any quantum system that utilises an optical approach, either by using entangled photons or interacting with atoms or ions, can be likely to benefit from the use of PICs. “This really includes an


extremely large number of applications and systems, such as atomic clocks, quantum magnetometers, atom interferometers, quantum imaging and remote sensing, Rydberg receivers, quantum computers, random number generators, quantum networks and others,” he says. “And then these systems can be utilised in various commercial and defence markets, so opportunities are extremely broad.”


Quantum photonic integration – what’s the timeline? When it comes to the timeline and rate of adoption of quantum technologies, Komljenovic observes that it is an ‘emerging market’ with development funding and support drawn


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from both venture capital and government sources. Although he says predicting the future is challenging “due to the inherent uncertainty and complexity”, he believes the next three years “should show the path where both Nexus Photonics PICs and quantum systems become more widespread, and are eventually deployed in our everyday lives, either to support sensing, healthcare, security or some other market”. “Acceleration will likely


require a consolidation of approaches to achieve quantum systems. Today, quantum is fragmented, as there are multiple modalities of how certain functionality can be achieved and we still don’t know which one is best in terms of system performance, including end cost,” he says. As this consolidation


emerges, Komljenovic says Nexus technology can help scaling by providing advanced, fully integrated PICs with on-chip sources “that can be mass manufactured using CMOS-like processes. This can enable drastic reduction in size, weight, power and cost, which is necessary for mass deployment of any system”. According to Merzbacher, some quantum technologies, including quantum sensors for measuring gravity and electromagnetic fields, as well as atomic clocks for precise timekeeping, are available today. However, the current markets “are relatively small and will only grow if the technologies provide a practical advantage in large market segments such as the automotive sector”. “The steady progress


reported in quantum computing is encouraging,” she told Electro Optics. “Early use cases may be targeted, and the rate of adoption will be accelerated by close collaboration between end users and developers.” Meanwhile, Sidqi points


out that the various types of quantum technologies are all at different maturity stages and, apart from a few sensing and imaging technologies – including single-photon imaging, photon detection


March 2024 Electro Optics 23


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