LightOn Qore in a Nutshell
Tags: Quantum Computing, Photonics

At LightOn, we recently announced a future quantum product called Qore. This blog post explains what this new product is and how it is a radical departure from traditional approaches to Quantum Computing. You may want to read the initial press release.

LightOn Qore Architecture

LightOn Qores are an efficient and innovative way of implementing linear operations on quantum resources, which is an essential building block for photonic quantum computing. The devices are compatible with high quality off-chip sources and detectors and unlike other approaches, do not introduce significant interfacing losses. LightOn Qores are a compact, integrated and more scalable adaptation of the apparatus first described in a Nature Photonics paper , originating from one of our co-founders research group [1]. Rather than using lossy photonic waveguides, light propagates in distinct spatial modes of highly multimodal fibers (>1000 modes) that serve as computational railings. Light that is coming through each input port is coupled to the spatial modes of the fiber. The linear operation is instantiated by tuning a spatial light modulator. Each railings output are then eventually coupled to single photon detectors or homodyne detection systems so as to implement a specific algorithm.

Much like what they say in Real-Estate, the advantages of this new resource are: scalability, scalability, scalability.

Scalability in the number of quantum operations: the use of standard optical fibers means that the most efficient quantum sources and detectors can be interfaced with the device with limited photon loss — there is, for instance, no need to couple into waveguides, which is a key challenge in quantum integrated circuits. This limited loss property enables the implementation of more complex algorithms that require a larger number of detection events.

Scalability in the physical size and functional complexity: In Qores, the loss is independent from the path taken by the quantum state or the operation implemented on the device! Once the Qore device is calibrated, the interaction can be tuned at the rate of the light modulator (currently about 10Hz) independently of the circuit size. Although modest when compared to the tunability rate of a single phase shifter, insensitivity to circuit size brings a massive competitive advantage at larger scales. The addition of railings is possible simply through an expansion of the modulation estate and as a result the thermal power density can remain almost constant for very large circuits.

Scalability in Ubiquity: Qore devices are agnostic. They can integrate with most Linear Optical Quantum Computing (LOQC) protocols whether circuit-based [2] or measurement-based [3] and can be used in discrete variable and continuous variable frameworks. Qore devices can also be easily adapted to a wide range of working wavelengths from the visible to the telecom range, while the dimension of the circuit can be tuned to cater to user preferences. The compact size of the devices makes them amenable to sequential quantum computing in a modular way. Although Qore devices can be used for quantum computing, they can also be adapted to quantum communication schemes such as quantum key distribution, quantum state resource characterisation and may even find a number of other quantum applications where linear reconfigurable circuits are needed.

What can the Qore device do?

The first generation of Qore devices will provide 8 input fiber ports where quantum states can be coupled into 19 distinct railings. The device is thus particularly suited to path-encoded qubit computations. For instance, 8 incoming single photons can be converted into 8 path-encoded qubits through their coupling onto 16 railings inside the fiber yielding a 16x16 unitary operation. Additional output ports can be used for heralding or controlling of the operation. The Qore devices are designed to bring new possibilities to the LOQC field. In that context, their modular nature may enable their use in conjunction with other systems to harness the advantages of existing architectures.

This first generation of LightOn Qore devices represents the first steps in meeting the scaling requirements for reconfigurable devices suitable for quantum advantage demonstrations.

LightOn Qores will be available in Q2 2022, please register here to hear more about the device in the future.

References:

[1] Lee et. al. Nature Photonics 14, 139–142 (2020)

[2] Knill et. al., Nature 409, 46–52 (2001)

[3] Raussendorf et. al. Physical Review Letter 86, 5188–5191 (2001)

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The author

Adrien Cavaillès, Lead Quantum Computing at LightOn