Today's most advanced quantum computers are trapped in a deep freeze, limited to about 1,000 qubits because the refrigerators that keep them cold cannot handle more heat from the control cables. The problem is that Google and IBM's superconducting qubits operate at microwave frequencies—a few billion cycles per second—and must be kept colder than outer space. The only refrigerators capable of this have limited cooling power, and the copper cables used to control the qubits add unwanted heat, capping the system at roughly 1,000 qubits. Real-world applications in medicine and materials discovery will require millions. This project aims to break that bottleneck by shifting quantum computing to terahertz frequencies—thousands of times higher than microwaves. The researcher has devised a light-based system to generate these high frequencies, which would allow the qubits to operate at warmer temperatures. Replacing electrical cables with optical fibres would also eliminate the heat problem. If successful, these changes could scale quantum computers from thousands to hundreds of millions of qubits, making them powerful enough to simulate complex chemical and biological reactions that traditional computers cannot handle.
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Quantum computers could be useful for simulating biological and chemical reactions beyond the reach of traditional computers. Among many other advances, this will revolutionise medicine and materials discovery. Various technologies are explored for quantum computing. For example, superconductors used by Google and IBM rely on qubits, two-level quantum systems with distinct energy spacing. To solve real-world problems, arrays of millions of qubits are needed. This current implementation, operating at microwave frequencies (a few GHz), demands colder temperatures than even outer space - and the only refrigerators that can support this have limited cooling power. Higher frequencies would allow an increased working temperature, although different superconducting materials would also be needed. Furthermore, copper cables for controlling the qubit arrays electrically introduces unwanted heat, limiting the refrigerator’s capacity to support around 1000 qubits. I aim to develop the enabling technology needed to realise a scalable quantum computer operating at THz frequencies. I propose two solutions: replacing electrical cables with optical fibres for control-signal distribution, and elevating working frequencies to the THz range. Generating high frequencies is challenging; however, I have devised a light-based system to achieve this leap, enabling operation at higher temperatures. These shifts allow the use of cooling technologies with greater power, potentially scaling the quantum technology to hundreds of millions of qubits.
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