Research

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].

Worldwide heating measurements of trapped ions