Our group
has several research projects involving various aspects of
controlling trapped atomic ions and individual photons for quantum information
purposes. Projects include:
Six
ions confined in a linear rf trap. The four bright ions (#1,#3,#5,#6) are 113Cd
, the other two (#2, #4) are 111Cd.
A general description of our research follows.
The Atomic Cd+ Qubit
Much of our work deals
with the atomic cadmium ion. The relevant atomic structure for 111Cd+ appears below. Two
hyperfine ground states such as the 1st-order magnetic field
insensitive F=1,m=0 and F=0, m=0 states can serve as a quantum bit
(qubit).
The state of the hyperfine qubit is measured with a resonant
circularly-polarized laser beam tuned near 214.5 nm that strongly scatters light in a cycling transition from the (1,0)
state [left], but scatters very little from the (0,0) state by
virtue of the large detuning [right]. Taken together, this
represents a near-perfect quantum efficient measurement of the
qubit state (quantum efficiency ~99.7%
in the data below).
The state of the hyperfine qubit can be coherently manipulated
using either a magnetic dipole transition driven by applied 14.53
GHz microwaves [left], or a two-photon stimulated Raman transition
driven by a pair of laser
beams having a 14.53 GHz beat note [right].
By repeating a sequence
of: (i) qubit preparation through optical pumping, (ii) coherent
manipulation with microwaves ot Raman beams for time t, and (iii) measurement of the qubit
state (the probability of the qubit to be in one of its two
states), while incrementing the time t, "single shot" coherent Rabi
flopping can be recorded (below), making the inherent noise due to
quantum measurement particularly vivid [below].
