# Previous Michelson Postdoctoral Prize Lectureships

## Monday, May 10, 2010 , 12:30 p.m. in Miller Room

David Hanneke, NIST

#### Entangled Mechanical Oscillators and a Programmable Quantum Computer: Adventures in Coupling Two-Level Systems to Quantum Harmonic Oscillators

The two-level system and the harmonic oscillator are among the simplest
analyzed with quantum mechanics, yet they display a rich set of behaviors.
Quantum information science is based on manipulating the states of two-level
systems, called quantum bits or qubits. Coupling two-level systems to
harmonic oscillators allows the generation of interesting motional states.
When isolated from the environment, trapped atomic ions can take on both of
these behaviors. The two-level system is formed from a pair of internal
states, which lasers efficiently prepare, manipulate, and read-out. The
ions' motion in the trap is well described as a harmonic oscillator and can
be cooled to the quantum ground state.
In this lecture, I will describe a complete set of methods for scalable ion
trap quantum information processing and their use in a programmable
two-qubit quantum processor. The qubits are stored in two beryllium
hyperfine states that are insensitive to magnetic field fluctuations. They
have coherence times hundreds of times longer than a typical experiment
lasts. Two beryllium ions are stored simultaneously with two magnesium ions,
which allow recooling the ions' motion without destroying any quantum
information. Segmented trap electrodes allow separation of parts of the ion
chain for quantum information transport and for individual laser-addressing
for single-qubit gates. An arbitrary quantum operation on two qubits can be
described with 15 real numbers, and we implement a quantum circuit composed
of one and two-qubit gates with sufficient input parameters that it can be
programmed to implement any operation.
Along the way, we use some of the above techniques to entangle spatially
separated mechanical oscillators, consisting of the vibrational states of
two pairs of ions held in different locations.

Download David's Slides for this talk.

Download David's Slides for this talk.

Host: Harsh Mathur