Abstract We have proposed two schemes to exhibit -antisymmetry in a four-level N-type atomic system interacting with two strong driving fields and a weak probe field. For both the schemes, the required spatially modulated coherence rendering -antisymmetry is achieved by employing a double-channel Gaussian beam for one driving field with a single channel for the other driving field in different field configurations. In each scheme, for equal and opposite detunings of the double-channel Gaussian beam, -antisymmetry can be obtained in the spatial domain. Such a way of control is unique to this model. Using the present method, it is possible to obtain -antisymmetry for both the homogeneously and inhomogeneously broadened atoms.
Abstract We present the interesting result that under sinusoidal field detuning setting along the propagation direction of 1D atomic lattices, the probe susceptibility response of the lattices, regardless of atomic configuration, uniformly demonstrates pseudo - P T - antisymmetry, which by our definition corresponds to n(z) = −n * (−z), the complex refractive index antisymmetry along propagation axis, and when being cast back to quantum mechanical side, corresponds to V(x,t) = −V * (x,−t), the conjugate time-reversal antisymmetry of complex potential. We define this as the pseudo - P T - antisymmetry, and prove the reason for this phenomenon to be the quantum-mechanical nature described by master equation under weak field approximation for any configuration of 1D atomic lattices. This work will help to deepen the understanding of origin of optical response features of atomic lattices, and will certainly open up the gate to a more rigorous, durable and flexible method of atomic optical lattice design .
We investigate the use of a single generalized dephasing qubit for sensing a quantum reservoir, where the antisymmetry of the coupling between the qubit and its reservoir is broken. Our results indicate that, in addition to the decay factor encoding channel, the antisymmetry breaking coupling introduces another phase factor encoding channel. We propose an optimal measurement strategy for the generalized dephasing qubit, which enables the practical measurement precision to reach the theoretical ultimate precision quantified by the quantum signal-to-noise ratio (QSNR). As an application example, the generalized dephasing qubit is employed to estimate the
s-wave scattering length of an atomic Bose-Einstein condensate. It is found that the QSNR contributed by the antisymmetry breaking coupling is at least two orders of magnitude higher than the QSNR contributed by the antisymmetry coupling at the millisecond timescale, and the optimal relative error can achieve a scaling $\ensuremath{\propto}1/(\ensuremath{\chi}t)$ in long-term encoding, where $\ensuremath{\chi}$ represents the relative driving strength and
t is the encoding time. Our work opens a way for supersensitive sensing of quantum reservoirs.