Emulation of a Quantum Spin with a Superconducting Phase Qudit

Higher-Level Quantum Emulation At the heart of a quantum computer is the device on which information is to be encoded. This is typically done with a qubit, a two-level quantum system analogous to the two-level bit that encodes 0 and 1 in classical computers. However, there need not be just two quantum energy levels. There could be three (a qutrit), or more generally, d -levels (a qudit) in the device. Neeley et al. (p. 722 ; see the Perspective by Nori ) demonstrate a five-level quantum device and show that their qudit can be used to emulate the processes involved in manipulating quantum spin. The use of multilevel qudits may also have potential in quantum information processing by simplifying certain computational tasks and simplifying the circuitry required to realize the quantum computer itself.