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E. A. Hinds

Publications and source records attributed to E. A. Hinds.

At least 91 records · Page 5Linked to original sources
arXiv2007

The effect of self-affine fractal roughness of wires on atom chips

Atom chips use current flowing in lithographically patterned wires to produce microscopic magnetic traps for atoms. The density distribution of a trapped cold atom cloud reveals disorder in the trapping potential, which results from meandering current flow in the wire. Roughness in the edges of the wire is usually the main cause of this behaviour. Here, we point out that the edges of microfabricated wires normally exhibit self-affine roughness. We investigate the consequences of this for disorder in atom traps. In particular, we consider how closely the trap can approach the wire when there is a maximum allowable strength of the disorder. We comment on the role of roughness in future atom--surface interaction experiments.

quant-ph↗
arXiv2007

On the feasibility of studying vortex noise in 2D superconductors with cold atoms

We investigate the feasibility of using ultracold neutral atoms trapped near a thin superconductor to study vortex noise close to the Kosterlitz-Thouless-Berezinskii transition temperature. Alkali atoms such as rubidium probe the magnetic field produced by the vortices. We show that the relaxation time $T_1$ of the Zeeman sublevel populations can be conveniently adjusted to provide long observation times. We also show that the transverse relaxation times $T_2$ for Zeeman coherences are ideal for studying the vortex noise. We briefly consider the motion of atom clouds held close to the surface as a method for monitoring the vortex motion.

cond-mat.other↗
arXiv2006

A supersonic beam of cold lithium hydride molecules

We have developed a source of cold LiH molecules for Stark deceleration and trapping experiments. Lithium metal is ablated from a solid target into a supersonically expanding carrier gas. The translational, rotational and vibrational temperatures are 0.9(0.1) K, 5.9(0.5) K and 468(17) K respectively. Although they have not reached thermal equilibrium with the carrier gas, we estimate that 90% of the LiH molecules are in the ground state, X^{1} Σ^{+} (v=0, J=0). With a single 7 ns ablation pulse, the number of molecules in the ground state is 4.5(1.8)*10^{7} molecules per steradian. A second, delayed, ablation pulse produces another LiH beam in a different part of the same gas pulse, thereby almost doubling the signal. A long pulse, lasting 150 microseconds, can make the beam up to 15 times more intense.

physics.atom-ph↗
arXiv2006

Probing the electron EDM with cold molecules

We present progress towards a new measurement of the electron electric dipole moment using a cold supersonic beam of YbF molecules. Data are currently being taken with a sensitivity of $10^{-27}\textrm{e.cm}/\sqrt{\textrm{day}}$. We therefore expect to make an improvement over the Tl experiment of Commins' group, which currently gives the most precise result. We discuss the systematic and statistical errors and comment on the future prospect of making a measurement at the level of $10^{-29}\textrm{e.cm}/\sqrt{\textrm{day}}$.

physics.atom-ph↗
arXiv2006

Comment on `Spin Decoherence in Superconducting Atom Chips'

We comment on a recent paper [Phys. Rev. Lett. 97, 070401 (2006): quant-ph/0603229] concerning rubidium atoms trapped near a superconducting niobium surface at ~4K. This seeks to calculate the rate of atomic spin flips induced by thermal magnetic noise. We point out that the calculation is in error by a large factor because it is based on the two-fluid model of superconductivity. This model gives a poor description of electromagnetic dissipation just below the critical temperature because it cannot incorporate the case II coherences of a fuller quantum theory.

quant-ph↗
arXiv2006

Towards quantum computing with single atoms and optical cavities on atom chips

We report on recent developments in the integration of optical microresonators into atom chips and describe some fabrication and implementation challenges. We also review theoretical proposals for quantum computing with single atoms based on the observation of photons leaking through the cavity mirrors. The use of measurements to generate entanglement can result in simpler, more robust and scalable quantum computing architectures. Indeed, we show that quantum computing with atom-cavity systems is feasible even in the presence of relatively large spontaneous decay rates and finite photon detector efficiencies.

quant-ph↗
arXiv2005

Bose-Einstein Condensation on a Permanent-Magnet Atom Chip

We have produced a Bose-Einstein condensate on a permanent-magnet atom chip based on periodically magnetized videotape. We observe the expansion and dynamics of the condensate in one of the microscopic waveguides close to the surface. The lifetime for atoms to remain trapped near this dielectric material is significantly longer than above a metal surface of the same thickness. These results illustrate the suitability of microscopic permanent-magnet structures for quantum-coherent preparation and manipulation of cold atoms.

cond-mat.other↗
arXiv2005

Pyramidal micro-mirrors for microsystems and atom chips

Concave pyramids are created in the (100) surface of a silicon wafer by anisotropic etching in potassium hydroxide. High quality micro-mirrors are then formed by sputtering gold onto the smooth silicon (111) faces of the pyramids. These mirrors show great promise as high quality optical devices suitable for integration into MOEMS and atom chips. We have shown that structures of this shape can be used to laser-cool and hold atoms in a magneto-optical trap.

physics.atom-ph↗
arXiv2005

Stark shift of the $A^2Π_{1/2}$ state in $^{174}$YbF

We have measured the Stark shift of the $A^2Π_{1/2} - X^2Σ^+$ transition in YbF. We use a molecular beam triple resonance method, with two laser transitions acting as pump and probe, assisted by an rf transition that tags a single hyperfine transition of the X state. After subtracting the known ground state Stark shift, we obtain a value of $70.3(1.5) $Hz/(V/cm)$^2$ for the static electric polarizability of the state $A^2Π_{1/2}(J=1/2,f)$. From this we calculate a value $μ_e=2.46(3)$D for the electric dipole moment of the $A^2Π_{1/2}(v=0)$ state.

physics.atom-ph↗
arXiv2005

Microfabricated high-finesse optical cavity with open access and small volume

We present a novel microfabricated optical cavity, which combines a very small mode volume with high finesse. In contrast to other micro-resonators, such as microspheres, the structure we have built gives atoms and molecules direct access to the high-intensity part of the field mode, enabling them to interact strongly with photons in the cavity for the purposes of detection and quantum-coherent manipulation. Light couples directly in and out of the resonator through an optical fibre, avoiding the need for sensitive coupling optics. This renders the cavity particularly attractive as a component of a lab-on-a-chip, and as a node in a quantum network.

quant-ph↗
arXiv2005

Cold atoms in videotape micro-traps

We describe an array of microscopic atom traps formed by a pattern of magnetisation on a piece of videotape. We describe the way in which cold atoms are loaded into one of these micro-traps and how the trapped atom cloud is used to explore the properties of the trap. Evaporative cooling in the micro-trap down to a temperature of 1 microkelvin allows us to probe the smoothness of the trapping potential and reveals some inhomogeneity produced by the magnetic film. We discuss future prospects for atom chips based on microscopic permanent-magnet structures.

physics.atom-ph↗
arXiv2005

Integrated optical components on atom chips

We report on the integration of small-scale optical components into silicon wafers for use in atom chips. We present an on-chip fibre-optic atom detection scheme that can probe clouds with small atom numbers. The fibres can also be used to generate microscopic dipole traps. We describe our most recent results with optical microcavities and show that single-atom detection can be realised on an atom chip. The key components have been fabricated by etching directly into the atom chip silicon substrate.

physics.atom-ph↗
arXiv2004

Fabrication of micro-mirrors with pyramidal shape using anisotropic etching of silicon

Gold micro-mirrors have been formed in silicon in an inverted pyramidal shape. The pyramidal structures are created in the (100) surface of a silicon wafer by anisotropic etching in potassium hydroxide. High quality micro-mirrors are then formed by sputtering gold onto the smooth silicon (111) faces of the pyramids. These mirrors show great promise as high quality optical devices suitable for integration into MOEMS systems.

physics.optics↗
arXiv2004

Micron-sized atom traps made from magneto-optical thin films

We have produced magnetic patterns suitable for trapping and manipulating neutral atoms on a $1 μ$m length scale. The required patterns are made in Co/Pt thin films on a silicon substrate, using the heat from a focussed laser beam to induce controlled domain reversal. In this way we draw lines and "paint" shaped areas of reversed magnetization with sub-micron resolution. These structures produce magnetic microtraps above the surface that are suitable for holding rubidium atoms with trap frequencies as high as ~1 MHz.

cond-mat.soft↗
arXiv2004

Thermal spin flips in atom chips

We derive the spontaneous and thermal spin-flip rates for a neutral two-level ultra-cold atom that is coupled to a magnetic field. We apply this theory to an atom in the vicinity of a 2-layer cylindrical absorbing dielectric body surrounded by an unbounded homogeneous medium. An analytical expression is obtained for the spontaneous and thermal spin-flip rate in this particular geometry. The corresponding lifetime is then computed numerically. We compare these theoretical lifetimes to those measured by Jones et al. [M.P.A. Jones, C.J. Vale, D. Sahagun, B.V. Hall, and E.A. Hinds, Phys. Rev. Lett. {\bf 91}, 080401 (2003)]. We investigate how the lifetime depends on the materials (skin depths) of the cylindrical body. We also show how scaling of the dimensions of the cylindrical body affects the lifetime when (i) the distance from the wire to the atom is fixed and (ii) when the distance from the wire to the atom is scaled.

quant-ph↗
arXiv2004

Quantum gates and decoherence

In the lectures we will be concerned with some aspects of physical implementations of quantum gate operations which are necessary for quantum information processing. We will discuss two possible realizations. One of them is based on qubits being encoded in atomic degrees of freedom where the atoms are manipulated in optical lattices above atom chips. The other realization is based on photonic qubits and measurement-induced nonlinearities in linear optics. Both implementations have in common that their main decoherence mechanism is absorption in dielectric materials. The quantum theory of light in absorbing media and its implications to decoherence will form the last part of the lectures.

quant-ph↗
arXiv2003

Slowing heavy, ground-state molecules using an alternating gradient decelerator

Cold supersonic beams of molecules can be slowed down using a switched sequence of electrostatic field gradients. The energy to be removed is proportional to the mass of the molecules. Here we report deceleration of YbF, which is 7 times heavier than any molecule previously decelerated. We use an alternating gradient structure to decelerate and focus the molecules in their ground state. We show that the decelerator exhibits the axial and transverse stability required to bring these molecules to rest. Our work significantly extends the range of molecules amenable to this powerful method of cooling and trapping.

physics.atom-ph↗