Scalable Quantum Computing with Optical Links

Quantum computers have great potential to solve problems which are intractable on classical computers. However, quantum processors have not yet reached the required scale to run applications which outperform traditional computers. Leading hardware platforms, such as superconducting qubit based processors, will soon become bottlenecked by the physical constraints of their low temperature environments, and the expansion of quantum computers will necessitate quantum links between multiple processor modules. Optical frequencies offer the most promising path for these links due to their resilience to noise even at ambient temperature and the maturity of classical optical networks. However, required microwave-to-optics transducers cannot operate deterministically yet, which has widely been seen as a key challenge for their integration into fault-tolerant quantum computers. In this work, we examine implementations of optical links between cryogenic units that surpass the performance of individual cryogenic modules even with the performance of existing or near-term microwave-to-optics transducers. We show methods for these transducers to provide on-demand entanglement between separated quantum processors with high fidelity and lay out key steps for adoption of the technology including scaling transducer numbers and integration with other hardware. Finally, we discuss a number of architectures comprised of these links which can drive the expansion of quantum data centers to utility scale.