Papers by Joerg Schmiedmayer
arXiv (Cornell University), Sep 2, 2013
We created dense ensembles of negatively charged nitrogen-vacancy (NV-) centers in diamond by neu... more We created dense ensembles of negatively charged nitrogen-vacancy (NV-) centers in diamond by neutron and electron irradiation for applications in hybrid quantum systems and magnetometry. We characterize fluorescence intensity, optical and coherence properties of the resulting defects by confocal microscopy, UV/Vis and FTIR spectroscopy, optically detected magnetic resonance and small angle X-ray scattering. We find the highest densities of NVat neutron fluences on the order of 10 17 cm −2 and electron doses of 10 18 cm −2 , with spin resonance linewidths of 6 MHz. Lower electron energies increase the ratio of centers in the desired negative charge state to those in the neutral one. Annealing at 900 • C during the irradiation reduces the spin resonance linewidth. Electron irradiation furthermore results in substantially higher optical transparency compared to neutron irradiation.
Physical Review Letters, 2020
Stochastic Optimization - Seeing the Optimal for the Uncertain, 2011
Interference and Coherence in 1-d Bose-Einstein-Condensates 1 JOERG SCHMIEDMAYER, Atominstitut de... more Interference and Coherence in 1-d Bose-Einstein-Condensates 1 JOERG SCHMIEDMAYER, Atominstitut der Oesterreichischen Universitaeten, TU-Wien Employing RF induced adiabatic potentials [1] on AtomChips [2] enables coherent manipulation of trapped matter waves with high precision. Using our exceptionally smooth AtomChip potentials [3] we study 1d condensates at strong transversal confinement (>10kHz) and extreme aspect ratio up to 10000, which can be coherently split along their long axis [4]. Bringing the two split clouds together we observe interference between the two ensembles. The interference pattern itself is sensitive probe of the order parameter in the 1d quantum gas and allows detailed studies of its coherence properties: • It allows precise separation between 'condensed' and 'thermal' component • Adjusting the barrier between the separated ensembles we can study tunnel coupling and phase locking between two 1d condensates and employ phase noise thermometry to measure the local temperature. • Coherently splitting into two isolated systems with an initially fixed phase relation, we investigate the dynamics of the phase fluctuations of a 1d quantum gas, and their influence on the statistics of the interferences. • The evolution of the interference of coherently split quantum gas can be compared to completely separated, independently created 1d condensates. Furthermore the RF coupling allows many different potential shapes to be realized, including a 2d cylinder shaped trap. The later allows to create a 2d condensate with periodic boundary conditions which exhibits peculiar interference. In addition combining the AtomChip with a 1d optical lattice of 2d planes we observe coherent Blochoszillations close to the AtomChip surface [5], which gives us a new tool for coherent manipulation of 2d mesoscopic quantum gases.
Physical Review Letters, 2008
We demonstrate that virtual excitations of higher radial modes in an atomic Bose gas in a tightly... more We demonstrate that virtual excitations of higher radial modes in an atomic Bose gas in a tightly confining waveguide result in effective three-body collisions that violate integrability in this quasione-dimensional quantum system and give rise to thermalization. The estimated thermalization rates are consistent with recent experimental results in quasi-1D dynamics of ultracold atoms.
Physical Review A, 2010
We measure the two-point density correlation function of freely expanding quasicondensates in the... more We measure the two-point density correlation function of freely expanding quasicondensates in the weakly interacting quasi-one-dimensional (1D) regime. While initially suppressed in the trap, density fluctuations emerge gradually during expansion as a result of initial phase fluctuations present in the trapped quasicondensate. Asymptotically, they are governed by the thermal coherence length of the system. Our measurements take place in an intermediate regime where density correlations are related to near-field diffraction effects and anomalous correlations play an important role. Comparison with a recent theoretical approach described by Imambekov et al. yields good agreement with our experimental results and shows that density correlations can be used for thermometry of quasicondensates.
Physical Review A, 2009
We examine the possibility of coherent, reversible information transfer between solid-state super... more We examine the possibility of coherent, reversible information transfer between solid-state superconducting qubits and ensembles of ultra-cold atoms. Strong coupling between these systems is mediated by a microwave transmission line resonator that interacts near-resonantly with the atoms via their optically excited Rydberg states. The solid-state qubits can then be used to implement rapid quantum logic gates, while collective metastable states of the atoms can be employed for long-term storage and optical read-out of quantum information.
Optics Letters, 2006
We show that a low finesse cavity can be efficient for detecting neutral atoms. The low finesse c... more We show that a low finesse cavity can be efficient for detecting neutral atoms. The low finesse can be compensated for by decreasing the mode waist of the cavity. We have used a near concentric resonator with a beam waist of 12µm and a finesse of only 1100 to detect magnetically guided Rb atoms with a detection sensitivity of 0.1 atom in the mode volume. For future experiments on single atom detection and cavity QED applications, it should be very beneficial to use miniaturized optical resonator integrated on atom chips.
New Journal of Physics, 2010
Interferometry with ultracold atoms promises the possibility of ultraprecise and ultrasensitive m... more Interferometry with ultracold atoms promises the possibility of ultraprecise and ultrasensitive measurements in many elds of physics, and is the basis of our most precise atomic clocks. Key to a high sensitivity is the possibility to achieve long measurement times and precise readout. Ultra cold atoms can be precisely manipulated at the quantum level, held for very long times in traps, and would therefore be an ideal setting for interferometry. In this paper we discuss how the non-linearities from atom-atom interactions on one hand allow to efficiently produce squeezed states for enhanced readout, but on the other hand result in phase diffusion which limits the phase accumulation time. We find that low dimensional geometries are favorable, with two-dimensional (2D) settings giving the smallest contribution of phase diffusion caused by atom-atom interactions. Even for time sequences generated by optimal control the achievable minimal detectable interaction energy ∆E min is on the order of 10 −4 µ, where µ is the chemical potential of the BEC in the trap. From there we have to conclude that for more precise measurements with atom interferometers more sophisticated strategies, or turning off the interaction induced dephasing during the phase accumulation stage, will be necessary.
Journal of Physics: Conference Series, 2005
The magnetic trapping potentials for atoms on atom chips are determined by the current flow patte... more The magnetic trapping potentials for atoms on atom chips are determined by the current flow pattern in the chip wires. By modifying the wire shape using focused ion beam nano-machining we can design specialized current flow patterns and therefore micro-design the magnetic trapping potentials. We give designs for a barrier, a quantum dot, and a double well or double barrier and show preliminary experiments with ultra cold atoms in these designed potentials.
Applied Physics B, 2014
We report the realization of a robust magnetic transport scheme to bring > 3 × 10 8 ultracold 87 ... more We report the realization of a robust magnetic transport scheme to bring > 3 × 10 8 ultracold 87 Rb atoms into a cryostat. The sequence starts with standard laser cooling and trapping of 87 Rb atoms, transporting first horizontally and then vertically through the radiation shields into a cryostat by a series of normal-and superconducting magnetic coils. Loading the atoms in a superconducting microtrap paves the way for studying the interaction of ultracold atoms with superconducting surfaces and quantum devices requiring cryogenic temperatures.
Nature Physics, 2011
In recent years, substantial progress has been made in exploring and exploiting the analogy betwe... more In recent years, substantial progress has been made in exploring and exploiting the analogy between classical light and matter waves for fundamental investigations and applications 1. Extending this analogy to quantum matter-wave optics is promoted by the nonlinearities intrinsic to interacting particles and is a stepping stone towards non-classical states 2,3. In light optics, twin-photon beams 4 are a key element for generating the non-local correlations and entanglement required for applications such as precision metrology and quantum communication 5. Similar sources for massive particles have so far been limited by the multi-mode character of the processes involved or a predominant background signal 6-13. Here we present highly efficient emission of twin-atom beams into a single transversal mode of a waveguide potential. The source is a one-dimensional degenerate Bose gas 14 in the first radially excited state. We directly measure a suppression of fluctuations in the atom number difference between the beams to 0.37(3) with respect to the classical expectation, equivalent to 0.11(2) after correcting for detection noise. Our results underline the potential of ultracold atomic gases as sources for quantum matter-wave optics and should enable the implementation of schemes previously unattainable with massive particles 5,15-19. Binary collisions between atoms provide a natural means to generate dual number states of intrinsically correlated atoms 15. Experimental schemes include spontaneous emission of atom pairs by collisional de-excitation 9 or four-wave mixing 10-12. Stimulated emission into twin-modes has been demonstrated in seeded fourwave mixing 2,6 , and parametric amplification in optical lattices 7,8 or spinor condensates 13. Among these schemes, suppression of relative number fluctuations could so far be demonstrated only for multi-mode twin-atoms 12. A different route to non-classical states is provided by ensembles in multi-well potentials that become number-squeezed during their time evolution 20,21. Here, we demonstrate how collisional de-excitation of a onedimensional degenerate Bose gas can be used to efficiently create matter-wave beams of twin-atoms. The restricted geometry of a waveguide potential forces emission of the beams into a single transversal mode, in analogy to an optical parametric amplifier 4. We prepare the initial population inversion to a radially excited state by shaking the trap, employing an optimal control strategy. Time-of-flight fluorescence imaging is used to directly observe the suppressed relative number fluctuations in the emitted beams. The starting point of our investigations is a dilute, quantum degenerate gas of neutral rubidium-87 atoms magnetically trapped in a tight waveguide potential with a shallow axial harmonic confinement (ν x = 16.3 Hz) on an atom chip 22. Our scheme
Understanding non-equilibrium dynamics of many-body quantum systems is crucial for many fundament... more Understanding non-equilibrium dynamics of many-body quantum systems is crucial for many fundamental and applied physics problems ranging from de-coherence and equilibration to the development of future quantum technologies such as quantum computers which are inherently non-equilibrium quantum systems. One of the biggest challenges is that there is no general approach to characterize the resulting quantum states.
We present new ways of trapping a neutral atom with static electric and magnetic fields. We discu... more We present new ways of trapping a neutral atom with static electric and magnetic fields. We discuss the interaction of a neutral atom with the magnetic field of a current carrying wire and the electric field of a charged wire. Atoms can be trapped by the 1/r magnetic field of a current-carrying wire in a two-dimensional trap. The atoms move in Kepler-like orbits around the wire and angular momentum prevents them from being absorbed at the wire. Trapping was demonstrated in an experiment by guiding atoms along a 1 m long current-carrying wire. Stable traps using the interaction of a polarizable atom with the electric field of a charged wire alone are not possible because of the 1/r 2 form of the interaction potential. Nevertheless, we show that one can build a microscopic trap with a combination of a magnetic field generated by a current in a straight wire and the static electric field generated by a concentric charged ring which provides the longitudinal confinement. In all of these traps, the neutral atoms are trapped in a region of maximal field, in their high-field seeking state.
Scientific reports, Jan 24, 2016
In this article we present a simple repeater scheme based on the negatively-charged nitrogen vaca... more In this article we present a simple repeater scheme based on the negatively-charged nitrogen vacancy centre in diamond. Each repeater node is built from modules comprising an optical cavity containing a single NV(-), with one nuclear spin from (15)N as quantum memory. The module uses only deterministic processes and interactions to achieve high fidelity operations (>99%), and modules are connected by optical fiber. In the repeater node architecture, the processes between modules by photons can be in principle deterministic, however current limitations on optical components lead the processes to be probabilistic but heralded. Our resource-modest repeater architecture contains two modules at each node, and the repeater nodes are then connected by entangled photon pairs. We discuss the performance of such a quantum repeater network with modest resources and then incorporate more resource-intense strategies step by step. Our architecture should allow large-scale quantum information n...
Phys Rev Lett, 2007
We demonstrate a novel way to efficiently and very robust create an entanglement between an atomi... more We demonstrate a novel way to efficiently and very robust create an entanglement between an atomic and a photonic qubit. A single laser beam is used to excite one atomic ensemble and two different spatial modes of scattered Raman fields are collected to generate the atom-photon entanglement. With the help of build-in quantum memory, the entanglement still exists after 20.5 $\mu$s storage time which is further proved by the violation of CHSH type Bell's inequality. Our entanglement procedure is the building block for a novel robust quantum repeater architecture [Zhao et al, Phys. Rev. Lett. 98, 240502 (2007)]. Our approach can be easily extended to generate high dimensional atom-photon entanglements.
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Papers by Joerg Schmiedmayer