Superconducting Qubits: Dephasing and Quantum Chemistry
One of the most exciting potential applications of a quantum computer is the ability
to efficiently simulate quantum systems, a task that is out of the reach of even the
largest classical supercomputers. Such simulations require a quantum algorithm capable
of efficiently representing and manipulating a quantum system, as well as a device with
sufficient coherence to execute it. In this work, we describe experiments advancing both
of these goals. First, we discuss dephasing—currently a leading cause of decoherence
in superconducting qubits—and present measurements accurately quantifying both low-
and high-frequency phase noise sources. We then discuss two quantum algorithms for
the simulation of chemical Hamiltonians, and experimentally contrast their performance.
These results show that with continuing improvement in quantum devices we may soon
be able to apply quantum computers to practical chemistry problems.