quantum electro-optic amplifiers for the next generation quantum and supercomputers

Introduction

Quantum computers face many bottlenecks towards upscaling the number of qubits and increasing their computational power. One of them is the radio frequency (RF) bottleneck between the qubit processor inside the cryostat and the room temperature control and readout electronics.

Hybrid Solution

Like their classical counterparts, hope lies in replacing the RF links with optical fibers, resulting in a hybrid situation where:

• RF qubits will be used for computation
• Optical qubits will serve for remote communication

Current Challenges

However, electro-optical (EO) devices that parametrically amplify RF qubits directly to optical qubits and vice versa have thus far remained elusive.

Q-Amp Project

Q-Amp will demonstrate a new class of EO amplifiers that realize the required unity efficiency to achieve this goal. This is impossible with current EO architectures, which suffer from a deleterious trade-off between:

1. EO interaction strength (g)
2. EO losses (Q-factors)

This trade-off originates from their device design. Enhancing g requires bringing the RF superconducting circuit in close vicinity of the optical waveguide, which comes at the expense of excess EO losses.

Innovative Approach

To cope with this, we will pioneer a transparent EO device technology that enhances g without the need to bring superconductors and optical waveguides in close proximity. We will achieve this by:

• Concentrating the RF and the optical field in the same nanoscale interaction volume via dipolar screening in ferroelectrics and/or ballistic transport in graphene.

Confining both fields within next-generation EO materials will enable an increase of g from hundreds of Hz (prior art) to Megahertz levels. Simultaneously, light will be kept away from the lossy superconducting electrodes, enabling moderate Q-values of 1E5 to 1E6.

Conclusion

Q-Amp's EO amplifiers will finally overcome the scaling limitations of current superconducting quantum computers and will provide classical superconducting supercomputers with the high-speed EO gateways they desperately need.