Due to traveling by both myself and my research partner, this week’s progress was limited. The quantum paper for our reading group was entitled Circuit knitting with classical communication.

The paper addresses the challenge of limited qubits in quantum computing and introduces circuit knitting techniques to partition large quantum circuits into smaller subcircuits that can fit on available quantum devices. Specifically, it focuses on a method that uses quasiprobability simulation to simulate nonlocal gates, which act on qubits in different subcircuits.

The study shows that classical communication can significantly decrease the overhead required to simulate circuits with multiple nonlocal gates, such as CNOT gates. For example, by using classical communication, the overhead for simulating circuits with multiple nonlocal CNOT gates is reduced from O(9^n) to O(4^n). The research presents a novel technique utilizing bidirectional classical communication, leading to a more efficient simulation process.

The authors also investigate the use of this approach with different types of gates, including Clifford and controlled rotation gates, and provide analytic results for the optimal simulation overhead in various scenarios. They highlight that classical communication does not always help with single gate simulations but shows significant advantages when simulating circuits with multiple instances of the same gate. The paper concludes by discussing open questions and the potential practical applications of these techniques as quantum computers evolve.