Christopher M. Seck

Broadband optical cooling of molecular rotors from room temperature to the ground state

Laser cycling of resonances can remove entropy from a system via spontaneously emitted photons, with electronic resonances providing the fastest cooling timescales because of their rapid spontaneous relaxation. Although atoms are routinely laser-cooled, even simple molecules pose two interrelated challenges for cooling: every populated rotational-vibrational state requires a different laser frequency, and electronic relaxation generally excites vibrations. Here we cool trapped AlH(+) molecules to their ground rotational-vibrational quantum state using an electronically exciting broadband laser to simultaneously drive cooling resonances from many different rotational levels. Undesired vibrational excitation is avoided because of vibrational-electronic decoupling in AlH(+). We demonstrate rotational cooling on the 140(20) ms timescale from room temperature to 3.8(-0.3)(+0.9) K, with the ground-state population increasing from ~3 to 95.4(-2.1)(+1.3)%. This cooling technique could be applied to several other neutral and charged molecular species useful for quantum information processing, ultracold chemistry applications and precision tests of fundamental symmetries.

Rotational state analysis of AlH+ by two-photon dissociation

Abstract We perform ab initio calculations relevant to predict the cross-section of an experimentally accessible ( 1 + 1 ′ ) resonance-enhanced multiphoton dissociation (REMPD) pathway in AlH+. Experimenting on AlH+ ions held in a radiofrequency trap, we confirm dissociation via this channel with analysis performed using time-of-flight mass spectrometry, demonstrate the use of REMPD for rotational state analysis, and measure the rotational distribution of trapped AlH+ to be consistent with the expected thermal distribution. AlH+ is a particularly interesting species because its electronic level structure is compatible with proposals to perform rotational optical pumping, direct Doppler cooling, and single-molecule fluorescence detection. Potential applications of trapped AlH+ include searches for time-varying constants, quantum information processing, and ultracold chemistry studies.

Noise reduction of a Libbrecht--Hall style current driver

The Libbrecht-Hall circuit is a well-known, low-noise current driver for narrow-linewidth diode lasers. An important feature of the circuit is a current limit to protect the laser diode. As the current approaches the maximum limit, however, the noise in the laser current increases dramatically. This paper documents this behavior and explores simple circuit modifications to alleviate this issue.

Raman sideband cooling of a 138Ba+ ion using a Zeeman interval

Motional ground state cooling and internal state preparation are important elements for quantum logic spectroscopy (QLS), a class of quantum information processing. Since QLS does not require the high gate fidelities usually associated with quantum computation and quantum simulation, it is possible to make simplifying choices in ion species and quantum protocols at the expense of some fidelity. Here, we report sideband cooling and motional state detection protocols for

Raman sideband cooling of aBa+138ion using a Zeeman interval

^{138}

Raman sideband cooling of a Ba + 138 ion using a Zeeman interval

Ba

Raman sideband cooling of a 138Ba+ ion using a single Zeeman interval

^+

Raman sideband cooling of

of sufficient fidelity for QLS without an extremely narrowband laser or the use of a species with hyperfine structure. We use the two S

^{138}

_{1/2}

Ba

Zeeman sublevels of