Ultrafast Gates in Atomic - PowerPoint Presentation

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Ultrafast Gates in Atomic

Qubits

"Ultrafast Gates for Single Atomic Qubits," W. C. Campbell, J. Mizrahi, Q. Quraishi, C. Senko, D. Hayes, D. Hucul, D. N. Matsukevich, P. Maunz, and C. Monroe, Phys. Rev. Lett. 105, 090502 (2010).

An ion has internal energy levels that can serve as a

qubit

. The

qubit

begins in the down state ([0]). By absorbing and emitting photons from a single pulse (shown below) the qubit can be flipped to the up ([1]) state.

The pulse can be optically shaped to make any combination or superposition of the two qubit states: [1] and [0].

12.6 GHz

PFC experimentalists in the Trapped Ion Quantum Information group have performed a gate that flips the state of a single atomic

qubit

in less than 50 picoseconds. The time

to perform this same operation

with continuous wave (CW)

lasers,

a

standard for these types of atomic systems

, is typically over 10,000 times

slower.

In conventional computers a bit can

be in the state 0 or 1, but not both simultaneously.

By contrast, a quantum bit, or

qubit

,

can reside in a combination of the

two

states.

Qubits

can made from any quantum system having two energy levels. In this experiment, the qubit is a laser cooled, singly ionized Ytterbium atom having two ground state electronic levels labeled [1] and [0], or up and down. The state of this system can be controllably manipulated with lasers or microwave radiation.

The researchers drive

qubit

rotations using a highly energetic

single

pulse

or

by optically dividing the pulse

into two counterpropagating

pulses. The gate, whether performed with CW or pulsed lasers, is a process that requires two photons. Here, the

key technology is

an

ultraviolet laser that emits

a pulse

of

light

that is 10 picosecond long

every 8

nanoseconds. Within each individual pulse there are photons that have the frequency separation required (12.6 GHz) to coherently manipulate the

qubit

.