Suppression and enhancement of decoherence in an atomic Josephson junction
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Suppression and enhancement of decoherence in an atomic Josephson junction

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CC Attribution 3.0 Unported:
You are free to use, adapt and copy, distribute and transmit the work or content in adapted or unchanged form for any legal purpose as long as the work is attributed to the author in the manner specified by the author or licensor. 
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2016

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English

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Abstract 
We investigate the role of interatomic interactions when a Bose gas, in a doublewell potential with a finite tunneling probability (a 'Bose–Josephson junction'), is exposed to external noise. We examine the rate of decoherence of a system initially in its ground state with equal probability amplitudes in both sites. The noise may induce two kinds of effects: firstly, random shifts in the relative phase or number difference between the two wells and secondly, loss of atoms from the trap. The effects of induced phase fluctuations are mitigated by atom–atom interactions and tunneling, such that the dephasing rate may be suppressed by half its singleatom value. Random fluctuations may also be induced in the population difference between the wells, in which case atom–atom interactions considerably enhance the decoherence rate. A similar scenario is predicted for the case of atom loss, even if the loss rates from the two sites are equal. We find that if the initial state is numbersqueezed due to interactions, then the loss process induces population fluctuations that reduce the coherence across the junction. We examine the parameters relevant for these effects in a typical atom chip device, using a simple model of the trapping potential, experimental data, and the theory of magnetic field fluctuations near metallic conductors. These results provide a framework for mapping the dynamical range of barriers engineered for specific applications and set the stage for more complex atom circuits ('atomtronics').

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this paper is about the coherence of anatomic Josephson junction in the presence of external noise the dynamics of a BoseEinstein condensate of many atoms in the doublewell potential is equivalent to a Josephson junction of 2 superconductors with the tunneling barrier between them the
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system can be thought of as an ensemble of many twolevel systems represented by the loss fear a state where most of the atoms are in the right will is represented by a distribution in the south pole while state where most of the atoms are in the left will use is represented by a distribution near the north pole the ground state is usually a state where the population of the 2 wells is equal and represented by a distribution near the equator if the items are not interact and then the ground state is a coherent state where each outcomes is in a superposition of the 2 wells equally however in the presence of repulsive interactions in the ground state is partially localized state where some of the atoms are mainly Manuel and some of the up atoms are mainly in the other this means that a phase difference applied between the whales will cause less transfer of population between the whales then in the case of a noninteracting system the bluffs cheerleader wafer can be reduced into a flat phase number space in the face
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number playing this looks like our numbers squeezed state where the Fe dissolution is stressed and their number distribution is squeezed by a factor of CSI what happens when an external noises induces phase difference fluctuations between the 2 wells we describe the evolution of a random walk process of phase jumps combined with Hamiltonian evolution in the
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doublewell trap the different colors in the wells represent the difference in phases between the whales phase jump is followed by a 2 that some oscillation dynamics where their phase difference transforms into a number difference but the number difference is much smaller then their memory France in a noninteracting system due to lease numbers squeezing affect affect the rate of loss of
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coherence is proportional to their the rate of growth of the sum of squares of the number of fluctuations in the phase fluctuations so that in the case of number squeezing the rate of lots of quiterons is suppressed by suppressed number fluctuations relative to the noninteracting case represented by the best serial what
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happens when atoms are lost from the trap in a noninteracting system each atom that is lost from 1 trap is also lost from the other crap equally but in the case of interactions but the loss of atoms from the and the
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traps creates number fluctuations these number fluctuations are translated into phase fluctuation but in these time due due to their squeezing effect the phase fluctuations created by the number of fracture lations are much larger than in the case of and noninteracting system this means that loss can induce the coherence and enhanced decoherence in there that system in this paper we discuss the effect of
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external noise and its interplay with the interactions between the atoms on and the decoherence of and was Ajan considered in double well especially in the context of magnetic fluctuations is very close to manhattan cheap