The goal of this research is to develop non-destructive, or lossless, quantum state detection methods for single trapped neutral atoms in order to realize robust neutral atom qubits. This work will directly address an important limitation in neutral atom qubit experiments, which is that quantum state detection of single atoms results in the loss of the qubit from the trap. This research will lead to increases in experimental efficiency for neutral atom systems and enable exciting new developments in the field of quantum information.
This research will advance the broader field of quantum information science, which represents a new information paradigm at the cross-roads of information science and physics that may lead to revolutionary new computing technologies benefiting all of society. Ultra-cold atoms and molecules provide one of the most promising experimental platforms for advancing the state of the art in quantum information science. The results from this research may also impact other technologically important applications of cold atom research, including precision sensors for navigation and magnetometry, atomic clocks and emerging quantum technologies.
The development of techniques to trap individual laser cooled atoms and ions have paved the way for many pioneering experiments in the field of quantum information processing and have enabled precision metrology of unprecedented accuracy. Quantum information science represents a new paradigm directly impacting the fields of information science and physics. Eventual developments may lead to revolutionary new computing technologies benefiting all of society. The success of cold atom quantum information experiments is due to the isolation of the trapped atom from external environmental perturbations and to the ability to initialize the quantum state of the atom and to subsequently read it out. In ion traps, the read-out of the quantum state of the ion has largely been done by direct detection of fluorescence, which does not significantly disturb the trapped ion. For neutral atom qubits, however, state detection of individual neutral atoms by fluorescence is destructive in the sense that the atoms are state-selectively ejected from the trap. Neutral atom qubit registers must therefore be rebuilt after every readout operation, which limits the experiments to a ~1 Hz repetition rate. In order to signifcantly advance the field of neutral atom quantum information processing, these rate limitations will need to be overcome. The primary objective of this research is to develop non-destructive, or lossless, quantum state detection methods for single trapped neutral atoms in order to realize robust neutral atom qubits. The particular focus of our recent work is the development of an efficient technique to characterize the trap-induced AC stark shifts for the typical case in which the differential shifts of the excited states are comparable to both the intrinsic linewidth of the transition and the shifts of the ground state. Our method is nondestructive in the sense that a single atom can be used to obtain the fluorescent spectrum of the entire excited-state manifold. It employs a continuous stream of short alternating probe and cooling pulses together with gated single-photon detection that provides high signal-to-noise ratio (>20) and an atom lifetime >60 s even for resonant probe detunings. Using this method, we measure the ac Stark shiftsof the D2 transitions in 87Rb for different trap depths and probe polarizations. The spectra are compared to theoretical calculations using independent measurements ofthe trap depth and atom temperature.