Towards Utility Scale Quantum Systems

To help elucidate fundamental limits on quantum measurement and feedback, we investigate the thermodynamic consequences of such operations in the context of fueling an engine. Critical to the engine's operation is the existence of a measurement observable that fails to commute with the system Hamiltonian. This non-commutation leads to a change in the system's energy. We present a microscopic engine based on qubits where local measurements break the binding energy of an entangled qubit pair—the resulting energy change that serves as the engine's fuel. We realize the engine using circuit-QED architecture with a chain of three transmon qubits. We study the energy and entropy transfers between system and measurement apparatus as well as the efficiency of the engine, determined by the ratio of energy extracted and the entropy produced.