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Register a new userSingle-photon cooling at the limit of trap dynamics: Maxwells Demon near maximum efficiency
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We demonstrate a general and efficient informational cooling technique for atoms which is an experimental realization of a one-dimensional Maxwells Demon. The technique transfers atoms from a magnetic trap into an optical trap via a single spontaneous Raman transition which is discriminatively driven near each atoms classical turning point. In this way, nearly all of the atomic ensembles kinetic energy in one dimension is removed. We develop a simple analytical model to predict the efficiency of transfer between the traps and provide evidence that the performance is limited only by particle dynamics in the magnetic trap. Transfer efficiencies up to 2.2% are reported. We show that efficiency can be traded for phase-space compression, and we report compression up to a factor of 350. Our results represent a 15-fold improvement over our previous demonstration of the cooling technique.
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Isotope separation is one of the grand challenges of modern society and holds great potential for basic science, medicine, energy, and defense. We consider here a new and general approach to isotope separation. The method is based on an irreversible change of the mass-to-magnetic moment ratio of a particular isotope in an atomic beam, followed by a magnetic multipole whose gradients deflect and guide the atoms. The underlying mechanism is a reduction of the entropy of the beam by the information of a single-scattered photon for each atom that is separated. We numerically simulate isotope separation for a range of examples, including lithium, for which we describe the experimental setup we are currently constructing. Simulations of other examples demonstrate this techniques general applicability to almost the entire periodic table. We show that the efficiency of the process is only limited by the available laser power, since one photon on average enables the separation of one atom. The practical importance of the proposed method is that large-scale isotope separation should be possible, using ordinary inexpensive magnets and the existing technologies of supersonic beams and lasers.
We present a quantitative model for magneto-optical traps operating on narrow transitions, where the transition linewidth and the recoil shift are comparable. We combine a quantum treatment of the light scattering process with a Monte-Carlo simulation of the atomic motion. By comparing our model to an experiment operating on the $5rm{s}^2~^1rm{S}_0 rightarrow 5rm{s}5rm{p}~^3rm{P}_1$ transition in strontium, we show that it quantitatively reproduces the cloud size, position, temperature and dynamics over a wide range of operating conditions, without any adjustable parameters. We also present an extension of the model that quantitatively reproduces the transfer of atoms into a far off-resonance dipole trap (FORT), highlighting its use as a tool for optimising complex cold atom experiments.
We report the cooling of an atomic ensemble with light, where each atom scatters only a single photon on average. This is a general method that does not require a cycling transition and can be applied to atoms or molecules which are magnetically trapped. We discuss the application of this new approach to the cooling of hydrogenic atoms for the purpose of precision spectroscopy and fundamental tests.
We propose and analyze Maxwells demon based on a single qubit with avoided level crossing. Its operation cycle consists of adiabatic drive to the point of minimum energy separation, measurement of the qubit state, and conditional feedback. We show that the heat extracted from the bath at temperature $T$ can ideally approach the Landauer limit of $k_BTln 2$ per cycle even in the quantum regime. Practical demon efficiency is limited by the interplay of Landau-Zener transitions and coupling to the bath. We suggest that an experimental demonstration of the demon is fully feasible using one of the standard superconducting qubits.
The first direct experimental replication of the Maxwell Demon thought experiment is outlined. The experiment determines the velocity/kinetic energy distribution of the particles in a sample by a novel interpretation of the results from a standard time-of-flight (TOF) small angle neutron scattering (SANS) procedure. Perspex at 293 K was subjected to neutrons at 82.2 K. The key result is a TOF velocity distribution curve that is a direct spatial and time-dependent microscopic probe of the velocity distribution of the Perspex nuclei at 293 K. Having this curve, one can duplicate the Demons approach by selecting neutrons at known kinetic energies. One example is given: namely, two reservoirs -- hot and cold reservoirs -- were generated from the 293 K source without disturbing its original 293 K energy distribution.
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