29 research outputs found
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Search for an electron electric dipole moment with trapped molecular ions
The search for a permanent electron electric dipole moment (eEDM) serves as a test of fundamental symmetry violations and of physics beyond the Standard Model. Trapped molecular ions in the 3Δ1 metastable electronic state are suitable candidates for an eEDM search due to their large effective electric fields and long electron spin coherence times. This thesis presents the quantum state manipulation and coherent spectroscopy of trapped HfF+ molecular ions in rotating bias fields for an eEDM search. The quantum state manipulation, which involves preparation of a large fraction of molecular ions in a single desired quantum state as well as rotational-state-resolved detection, is complicated by the lack of HfF+ spectroscopic information prior to the start of this thesis. We performed state preparation by first state-selectively autoionizing neutral HfF such that 35% of the HfF+ are formed in a single rovibrational level of the electronic ground state 1Σ+, and then transferring those ions into the desired Stark levels of a single hyperfine-rovibrational manifold of the 3Δ1 state. Rotational-state-resolved detection is accomplished by both laser-induced fluorescence and resonance-enhanced multi-photon photodissociation, where the latter is preferred as the state detection method of choice because its efficiency is two orders of magnitude higher compared to fluorescence. With the quantum state manipulation techniques developed, we performed Ramsey spectroscopy of the trapped HfF+ ions in the presence of rotating bias electric and magnetic fields, demonstrating electron spin coherence times as long as 150 ms. Finally, we present a preliminary measurement of the eEDM at the |de| < 10-25 e cm level.</p
Applications of correlated photon pairs : sub-shot noise interferometry and entanglement
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2006.Includes bibliographical references (p. 89-95).Using cesium atoms weakly coupled to a low-finesse cavity, we have generated photon pairs that are highly correlated in a non-classical way, as demonstrated by a large violation of the Cauchy-Schwartz inequality G = 760 +2100 -320 for a bin width T = 60 ns. Biphoton interferometry of the correlated pairs via the Holland-Burnett scheme holds promise to demonstrate precision beyond the shot noise limit, although the current interference fringe visibility of [beta]= 0.84 ± 0.04 only translates to a shot noise limited phase uncertainty. Polarization-time entangled pairs can also be directly generated, by optically pumping the atoms to both F = 3, mF = ±3 ground states. The degree of entanglement, expressed by the calculated fidelity f = 0.81 ± 0.09 and calculated Bell state parameter S = 2.3 ± 0.2, is estimated to be finite but not maximal.by Huanqian Loh.S.B
Coherent Microwave Control of Ultracold NaK Molecules
We demonstrate coherent microwave control of rotational and hyperfine states
of trapped, ultracold, and chemically stable NaK molecules.
Starting with all molecules in the absolute rovibrational and hyperfine ground
state, we study rotational transitions in combined magnetic and electric fields
and explain the rich hyperfine structure. Following the transfer of the entire
molecular ensemble into a single hyperfine level of the first rotationally
excited state, , we observe collisional lifetimes of more than , comparable to those in the rovibrational ground state, . Long-lived
ensembles and full quantum state control are prerequisites for the use of
ultracold molecules in quantum simulation, precision measurements and quantum
information processing.Comment: 5 pages, 4 figure
Laser-induced fluorescence studies of HfF+ produced by autoionization
Autoionization of Rydberg states of HfF, prepared using the optical-optical
double resonance (OODR) technique, holds promise to create HfF+ in a particular
Zeeman level of a rovibronic state for an electron electric dipole moment
(eEDM) search. We characterize a vibronic band of Rydberg HfF at 54 cm-1 above
the lowest ionization threshold and directly probe the state of the ions formed
from this vibronic band by performing laser-induced fluorescence (LIF) on the
ions. The Rydberg HfF molecules show a propensity to decay into only a few ion
rotational states of a given parity and are found to preserve their orientation
qualitatively upon autoionization. We show empirically that we can create 30%
of the total ion yield in a particular |J+,M+> state and present a simplified
model describing autoionization from a given Rydberg state that assumes no
angular dynamics.Comment: 8 pages, 5 figure
D1 magic wavelength tweezers for scaling atom arrays
D1 magic wavelengths have been predicted for the alkali atoms but are not yet
observed to date. We experimentally confirm a D1 magic wavelength that is
predicted to lie at 615.87 nm for Na, which we then use to trap and
image individual atoms with 80.0(6)% efficiency and without having to modulate
the trapping and imaging light intensities. We further demonstrate that the
mean loading efficiency remains as high as 74.2(7)% for a 1D array of eight
atoms. Leveraging on the absence of trap intensity modulation and lower trap
depths afforded by the D1 light, we achieve an order-of-magnitude reduction on
the tweezer laser power requirements and a corresponding increase in the
scalability of atom arrays. The methods reported here are applicable to all the
alkalis, including those that are attractive candidates for dipolar molecule
assembly, Rydberg dressing, or are fermionic in nature
Precision Spectroscopy of Polarized Molecules in an Ion Trap
Polar molecules are desirable systems for quantum simulations and cold
chemistry. Molecular ions are easily trapped, but a bias electric field applied
to polarize them tends to accelerate them out of the trap. We present a general
solution to this issue by rotating the bias field slowly enough for the
molecular polarization axis to follow but rapidly enough for the ions to stay
trapped. We demonstrate Ramsey spectroscopy between Stark-Zeeman sublevels in
180Hf19F+ with a coherence time of 100 ms. Frequency shifts arising from
well-controlled topological (Berry) phases are used to determine magnetic
g-factors. The rotating-bias-field technique may enable using trapped polar
molecules for precision measurement and quantum information science, including
the search for an electron electric dipole moment.Comment: Accepted to Scienc
Resonant dipolar collisions of ultracold molecules induced by microwave dressing
We demonstrate microwave dressing on ultracold, fermionic
NaK ground-state molecules and observe resonant dipolar
collisions with cross sections exceeding three times the -wave unitarity
limit. The origin of these collisions is the resonant alignment of the
approaching molecules' dipoles along the intermolecular axis, which leads to
strong attraction. We explain our observations with a conceptually simple
two-state picture based on the Condon approximation. Furthermore, we perform
coupled-channels calculations that agree well with the experimentally observed
collision rates. While collisions are observed here as laser-induced loss,
microwave dressing on chemically stable molecules trapped in box potentials may
enable the creation of strongly interacting dipolar gases of molecules.Comment: 6 pages, 4 figure
Proposal for observing Yang-Lee criticality in Rydberg atomic arrays
Yang-Lee edge singularities (YLES) are the edges of the partition function
zeros of an interacting spin model in the space of complex control parameters.
They play an important role in understanding non-Hermitian phase transitions in
many-body physics, as well as characterizing the corresponding non-unitary
criticality.Even though such partition function zeroes have been measured in
dynamical experiments where time acts as the imaginary control field,
experimentally demonstrating such YLES criticality with a physical imaginary
field has remained elusive due to the difficulty of physically realizing
non-Hermitian many-body models. We provide a protocol for observing the YLES by
detecting kinked dynamical magnetization responses due to broken PT symmetry,
thus enabling the physical probing of non-unitary phase transitions in
non-equilibrium settings. In particular, scaling analyses based on our
non-unitary time evolution circuit with matrix product states (tMPS) accurately
recover the exponents uniquely associated with the corresponding non-unitary
CFT. We provide an explicit proposal for observing YLES criticality in Floquet
quenched Rydberg atomic arrays with laser-induced loss, which paves the way
towards an universal platform for simulating non-Hermitian many-body dynamical
phenomena.Comment: 19 pages, 11 figure