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Scalable Quantum Optical Interconnects

Project description

Microwave-to-optical photon converters could enable scalable quantum computers

Microwave qubits are a fast-developing approach to quantum computing. However, the qubits are very sensitive to environmental disturbances, so they need to be kept at very low temperatures. Connecting the qubits into larger systems without losing their fragile quantum properties is challenging, limiting their use outside the laboratory. Optical photons have great potential in tackling this issue as they can propagate with low noise at room temperature. The EU-funded QUSCALE project plans to build scalable converters that transform microwave into optical qubits. The new converters are expected to enable larger quantum processors and networks, to a level where quantum computers perform useful tasks far beyond the ability of classical systems.


Coherent quantum systems are globally pursued in the race to build a compelling technology. One fast-developing approach uses high-fidelity microwave qubits. Major research efforts in academia and industry are demonstrating an elementary form of supremacy over classical technology by moving to tens and hundreds of such cryogenic qubits. However, it is currently impossible to connect the qubits well beyond a single refrigerator while preserving their fragile quantum properties – limiting their use outside the laboratory.

Optical photons, with their long-distance and near-noiseless propagation along room-temperature fibers, are uniquely placed to tackle this challenge. In QUSCALE, we will realize deployable converters between microwave and optical photons. We will build chips that convert between microwave and optical quantum information. The chips will let us increase the size of emerging quantum processors and networks to a level where we can perform useful tasks beyond the reach of classical systems.

To find use outside the laboratory, the converters must minimize the energy that is dissipated per converted qubit between microwaves and optics. Dissipated energy will determine whether microwave quantum processors can scale up via optics. We will achieve major reductions in the dissipated energy per converted qubit. The proposed devices will create a fundamentally new tool for physicists and engineers. They will enable a series of increasingly impactful networking tasks on the way to entanglement between distant microwave qubits, addressing an urgent need for optical interconnects between microwave quantum processors.


Net EU contribution
€ 2 047 500,00
412 96 Goteborg

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Södra Sverige Västsverige Västra Götalands län
Activity type
Higher or Secondary Education Establishments
Other funding
€ 0,00

Beneficiaries (2)