Cryogenic CMOS Circuits and Systems: Challenges and Opportunities in Designing the Electronic Interface for Quantum Processors

Quantum computing could potentially offer faster solutions for some of today's classically intractable problems using quantum processors as computational support for quantum algorithms [1]. Quantum processors, in the most frequent embodiment, comprise an array of quantum bits (qubits), the fundamental computational unit of a quantum computer. Unlike conventional bits, qubits can take a coherent state ranging from |0> to |1> on a continuous sphere, known as the Bloch sphere (Figure 1). When the state of the qubit, represented by a vector on the Bloch sphere, is on the equator of such a sphere, qubits are said to be in maximum superposition. Entanglement is the second important quantum mechanical property of qubit states, where knowing the state of one qubit implies knowing the state of the other one as well.