The Future of Quantum Computers: Influence of Photonics

Quantum computers (QCs) are machines that we can program to compute using their quantum nature. QCs have invented algorithms, showing that these machines can solve some problems more efficiently than classical digital computers. QC development has moved from academic laboratories to industrial settings in the last few years. Along with this has emerged a business ecosystem that connects technology developers with potential end-users, who are now present in virtually every industry.

The success of the quantum computing industry depends on building large-scale quantum computing hardware and commercially useful applications. Therefore, it is essential to choose the right hardware technology and reach the appropriate technical and commercial milestones within a reasonable time frame. Several teams worldwide are in a race to build quantum computers using a variety of platforms, including photonics, trapped ions, cold atoms, and superconducting circuits. Given the engineering complexity of the various technologies, we anticipate that photonics will play a central role in the realization of large-scale quantum computers, either for single-chip processors or to create a distributed computing system.

Distributed Quantum Computing

Currently, QC hardware projects focus on demonstrating devices with fewer than a hundred qubits, while the problems begin when we want to scale systems to thousands and eventually millions. Which technology platform has a better chance of scaling faster depends on the complexity of the hardware system and architecture. Modularity is a way to reduce system complexity, which, in the case of quantum computing, can be achieved through distributed connectivity of quantum chips via photonic interconnects. In addition to scalability, photonic networks provide the ability to connect all modules, resulting in a significant increase in the system’s computational power.

A modular approach to QC is already being developed for photonic and trap-ion platforms. Modularity can also be seen as a solution to overcome the scalability challenges and limitations of superconducting chip architecture. However, the problems of building a network either in cold microwave mode or with conversion to optical mode could undermine this solution option. Overall, superconductors are suitable for prototyping but not the best engineering choice for implementing large-scale QC.

Implementing a distributed QC requires its hardware and software infrastructure. So far, development has focused on single-chip quantum processors. Moving from a single processor to a distributed system requires several new developments, including the following.

• Optical/photonic networks: fibers, switches, frequency converters, synchronizers

• Quantum networking and entanglement distribution protocols and controllers

• Programming SDKs and compilers

• Fault-tolerant circuits and architecture

• Application partitioning and resource estimation

We believe this sets a solid new direction for research and development in quantum computing in the coming years.

Photonics for Information Processing

Beyond quantum computing, photonics technology will play a central role in developing the quantum Internet and cryptography. Beyond quantum applications, photonics already defines a new frontier in classical information processing, from low-power AI gas pedals to biosensors. Given its potential and dual-purpose, we consider photonics a low-risk, high-return technological investment in the quantum domain.