64 research outputs found
From megahertz to terahertz qubits encoded in molecular ions: theoretical analysis of dipole-forbidden spectroscopic transitions in N
Recent advances in quantum technologies have enabled the precise control of
single trapped molecules on the quantum level. Exploring the scope of these new
technologies, we studied theoretically the implementation of qubits and clock
transitions in the spin, rotational, and vibrational degrees of freedom of
molecular nitrogen ions including the effects of magnetic fields. The relevant
spectroscopic transitions span six orders of magnitude in frequency
illustrating the versatility of the molecular spectrum for encoding quantum
information. We identified two types of magnetically insensitive qubits with
very low ("stretched"-state qubits) or even zero ("magic" magnetic-field
qubits) linear Zeeman shifts. The corresponding spectroscopic transitions are
predicted to shift by as little as a few mHz for an amplitude of magnetic-field
fluctuations on the order of a few mG translating into Zeeman-limited coherence
times of tens of minutes encoded in the rotations and vibrations of the
molecule. We also found that the Q(0) line of the fundamental vibrational
transition is magnetic-dipole allowed by interaction with the first excited
electronic state of the molecule. The Q(0) transitions, which benefit from
small systematic shifts for clock operation and high sensitivity to a possible
variation in the proton-to-electron mass ratio, were so far not considered in
single-photon spectra. Finally, we explored possibilities to coherently control
the nuclear-spin configuration of N through the magnetically enhanced
mixing of nuclear-spin states
Non-destructive State Detection and Spectroscopy of Single Molecules
We review our recent experimental results on the non-destructive quantum-state detection and spectroscopy of single trapped molecules. At the heart of our scheme, a single atomic ion is used to probe the state of a single molecular ion without destroying the molecule or even perturbing
its quantum state. This method opens up perspectives for new research directions in precision spectroscopy, for the development of new frequency standards, for tests of fundamental physical concepts and for the precise study of chemical reactions and molecular collisions with full control
over the molecular quantum state
Identification of molecular quantum states using phase-sensitive forces
Quantum-logic techniques used to manipulate quantum systems are now increasingly being applied to molecules. Previous experiments on single trapped diatomic species have enabled state detection with excellent fidelities and highly precise spectroscopic measurements. However, for complex molecules with a dense energy-level structure improved methods are necessary. Here, we demonstrate an enhanced quantum protocol for molecular state detection using state-dependent forces. Our approach is based on interfering a reference and a signal force applied to a single atomic and molecular ion. By changing the relative phase of the forces, we identify states embedded in a dense molecular energy-level structure and monitor state-to-state inelastic scattering processes. This method can also be used to exclude a large number of states in a single measurement when the initial state preparation is imperfect and information on the molecular properties is incomplete. While the present experiments focus on N[Formula: see text], the method is general and is expected to be of particular benefit for polyatomic systems
Identification of molecular quantum states using phase-sensitive forces
Quantum-logic techniques used to manipulate quantum systems are now
increasingly being applied to molecules. Previous experiments on single trapped
diatomic species have enabled state detection with excellent fidelities and
highly precise spectroscopic measurements. However, for complex molecules with
a dense energy-level structure improved methods are necessary. Here, we
demonstrate an enhanced quantum protocol for molecular state detection using
state-dependent forces. Our approach is based on interfering a reference and a
signal force applied to a single atomic and molecular ion, respectively, in
order to extract their relative phase. We use this phase information to
identify states embedded in a dense molecular energy-level structure and to
monitor state-to-state inelastic scattering processes. This method can also be
used to exclude a large number of states in a single measurement when the
initial state preparation is imperfect and information on the molecular
properties is incomplete. While the present experiments focus on N, the
method is general and is expected to be of particular benefit for polyatomic
systems
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