We present the first experimental demonstration of a multiple-radiofrequency dressed potential for the configurable magnetic confinement of ultracold atoms. We load cold 87 Rb atoms into a double well potential with an adjustable barrier height, formed by three radiofrequencies applied to atoms in a static quadrupole magnetic field. Our multiple-radiofrequency approach gives precise control over the double well characteristics, including the depth of individual wells and the height of the barrier, and enables reliable transfer of atoms between the available trapping geometries. We have characterised the multiple-radiofrequency dressed system using radiofrequency spectroscopy, finding good agreement with the eigenvalues numerically calculated using Floquet theory. This method creates trapping potentials that can be reconfigured by changing the amplitudes, polarizations and frequencies of the applied dressing fields, and easily extended with additional dressing frequencies.PACS numbers: 67.85.Hj, 37.10.Gh, 03.75.Dg II. ATOMS IN A MULTI-COMPONENT RF FIELDThe dressed-atom picture of atom-radiation interaction [28,29] can be used to describe atoms trapped arXiv:1706.01491v2 [cond-mat.quant-gas]
Abstract.Methods to manipulate the individual constituents of an ultracold quantum gas mixture are essential tools for a number of applications, for example the direct quantum simulation of impurity physics. We investigate a scheme in which species-selective control is achieved using magnetic potentials dressed with multiple radiofrequencies, exploiting the different Landé g F -factors of the constituent atomic species. We describe a mixture dressed with two frequencies, where atoms are confined in harmonic potentials with a controllable degree of overlap between the two atomic species. This is then extended to a four radiofrequency scheme in which a double well potential for one species is overlaid with a single well for the other. The discussion is framed with parameters that are suitable for a 85 Rb and 87 Rb mixture, but is readily generalised to other combinations.arXiv:1701.05819v1 [cond-mat.quant-gas]
We present the effects of resonator birefringence on the cavity-enhanced interfacing of quantum states of light and matter, including the first observation of single photons with a time-dependent polarisation state that evolves within their coherence time. A theoretical model is introduced and experimentally verified by the modified polarisation of temporally-long single photons emitted from a 87 Rb atom coupled to a high-finesse optical cavity by a vacuum-stimulated Raman adiabatic passage (V-STIRAP) process. Further theoretical investigation shows how a change in cavity birefringence can both impact the atom-cavity coupling and engender starkly different polarisation behaviour in the emitted photons. With polarisation a key resource for encoding quantum states of light and modern micron-scale cavities particularly prone to birefringence, the consideration of these effects is vital to the faithful realisation of efficient and coherent emitter-photon interfaces for distributed quantum networking and communications.Cavity quantum electrodynamics (CQED) allows for the nature of light and matter to be interrogated through the enhanced interaction of an emitter with the resonant modes of a cavity [1][2][3]. This allows these fundamental interactions to be leveraged for quantum technologies [4][5][6][7][8] and, consequently, realising novel regimes in CQED has the potential to impact both foundational research and cutting-edge technological applications. Single photons are fundamental particles, they possess no deeper substructure, therefore it is tempting to consider their properties to be similarly immutable. However, CQED has shown photons to be a far richer resource, with a high degree of control demonstrated over the wavepackets [9], frequency [10], polarisation [11] and phase [12] of temporally-long single photons. Here, we report the first observation of a single-photon with a time-dependent polarisation state that evolves along its wavepacket. Moreover, this effect arises from a system increasingly prevalent in the pursuit of scalable quantum technologies.The coherent interfacing of light and matter qubits lies at the heart of many quantum networking proposals [4][5][6][7][8], and the interaction of atom-like emitters with a single photonic mode of a resonator provides a platform for realising this control. CQED is a vibrant field with single atoms and ions particularly suitable candidates with which to realise network nodes and singlephoton sources due to their inherently homogeneous nature. The a priori deterministic emission of single photons into well-defined quantum states has been realised in both atom-cavity [11, 14-17] and ion-cavity systems [18]. Proof-of-principle quantum networking demonstrations have leveraged this control to, for example, remotely entangle two atoms [19] and perform two-bit quantum gates [20][21][22]. Improving the efficiency and scalability of such systems ultimately requires increasing the strength and reliability of the emitter-cavity coupling, motivating the development of mic...
We have measured the damped motion of a trapped Bose-Einstein condensate, oscillating with respect to a thermal cloud. The cigar-shaped trapping potential provides enough transverse confinement that the dynamics of the system are intermediate between three-dimensional and onedimensional. We find that the scaling of the damping rate with temperature is consistent with Landau theory, but that the damping rate for axial oscillations at a given temperature is consistently smaller than expected for a three-dimensional gas. We attribute this to the suppressed density of states for low-energy transverse excitations (essential excitations for axial Landau damping), which results from the quantization of the radial motion.
We dress atoms with multiple-radiofrequency (RF) fields and investigate the spectrum of transitions driven by an additional probe field. A complete theoretical description of this rich spectrum is presented, in which we find allowed transitions and determine their amplitudes using the resolvent formalism. Experimentally, we observe transitions up to sixth order in the probe field using RF spectroscopy of Bose-Einstein condensates trapped in single-and multiple-RF-dressed potentials. We find excellent agreement between theory and experiment, including the prediction and verification of previously unobserved transitions, even in the single-RF case.
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