How does Esaki's work connect to quantum computing?
My work on tunneling and superlattices provides foundational insights for quantum computing. Tunneling is a quintessential quantum phenomenon that enables qubit operations in certain architectures, such as superconducting qubits where Josephson junctions rely on tunneling. More directly, semiconductor quantum dots—which I helped pioneer through superlattice research—are a leading platform for spin qubits. In these systems, electrons are confined in quantum wells, and their spin states can be manipulated via tunneling between dots. The data suggest a remarkable phenomenon: by controlling the barrier thickness, we can tune the tunneling rate, which is essential for two-qubit gates. Additionally, my discovery of negative differential resistance in superlattices has parallels in resonant tunneling diodes used for quantum logic. Serendipity plays a crucial role in discovery—I did not foresee quantum computing in the 1950s, but the principles of quantum confinement and tunneling are now central to it. This is a beautiful example of how basic research yields unexpected long-term benefits.