Opening a Remote Quantum Gate RESEARCH NEWS FROM

Opening a Remote Quantum Gate RESEARCH NEWS FROM THE PFC AT JQI P. Maunz, S. Olmschenk, D. Hayes, D. N. Matsukevich, L. -M. Duan, C. Monroe PFC-supported physicists have created and demonstrated a remote “quantum gate” – a key component for long-range quantum information transfer and an essential element of one plan for a quantum computer – by carefully manipulating the atomic states of two separately trapped ions. “Heralded Quantum Gate between Remote Quantum Memories, ” P. Maunz et al, Phys. Rev. Lett. 102, 250502 (2009) One indispensable part of any computer is a logic gate to perform operations on data. Researchers at the Joint Quantum Institute devised one by “entangling” two widely separated ytterbium ions. Entanglement is a uniquely quantum-mechanical condition in which the states of two or more objects become inextricably linked even if they are physically far apart. Prior to taking a measurement, each object exists in a “superposition” of many states at the same time. But when a measurement forces one entangled object to take on specific characteristics, the characteristics of the other object are automatically determined. The JQI gate design thus combines the function of a conventional electronic logic gate – which performs operations on single values of binary data bits – with the power of superposition, which allows multiple values in quantum bits, or “qubits, ” simultaneously. The design produces exactly the desired output for any chosen input about 90 percent of the time, and the team expects to improve the figure by increasing the photon detection rate.