We experimentally study the response of star-shaped clusters of initially unentangled N=4, 10, and 37 nuclear spin-1/2 moments to an inexact π-pulse sequence and show that an Ising coupling between the center and the satellite spins results in robust period-2 magnetization oscillations. The period is stable against bath effects, but the amplitude decays with a timescale that depends on the inexactness of the pulse. Simulations reveal a semiclassical picture in which the rigidity of the period is due to a randomizing effect of the Larmor precession under the magnetization of surrounding spins. The timescales with stable periodicity increase with net initial magnetization, even in the presence of perturbations, indicating a robust temporal ordered phase for large systems with finite magnetization per spin.

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We experimentally verify the Jarzynski and Wöjcik quantum heat exchange fluctuation relation by implementing the interferometric technique in liquid-state Nuclear Magnetic Resonance setup and study the exchange heat statistics between two weakly coupled spin-1/2 quantum systems. In presence of uncorrelated initial state with individual spins prepared in local Gibbs thermal states at different temperatures, the exchange fluctuation symmetry is verified for arbitrary transient time. In contrast, when the initial preparation includes correlation, the fluctuation symmetry breaks down and further leads to an apparent spontaneous flow of heat from cold to hot. Our experimental approach is general and can be systematically extended to study heat statistics for more complex out-of-equilibrium many-body quantum systems.Introduction.-Quantifying thermal and quantum fluctuations for mesoscopic and nanoscale systems are important both from fundamental and practical perspectives [1]. In the past two decades, considerable research have been devoted in developing a consistent theoretical framework to describe these fluctuations which have lead to the discovery of what is now collectively referred to as "fluctuation relations (FR)" [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. For out-ofequilibrium systems, classical or quantum, various thermodynamic observables such as work and heat are found to follow these universal relations either in the transient [5][6][7] and/or in the steady state regimes [16,17]. Apart from quantifying the probability of observing the rare events related to negative entropy production, fluctuation relations correctly describe systems residing at arbitrarily far-from-equilibrium and further serve as essential ingredient for establishing the rapidly growing field of quantum thermodynamics [19][20][21].Despite impressive theoretical progress, experimental verification of these FR's remained as a challenge in the quantum domain, primarily because of the requirement of projective measurements to construct the probability distribution function (PDF) for work/heat. In recent times, several experimental proposals have been put forward to construct such PDF [22][23][24][25][26][27][28]. Following projective measurement scheme, the first experimental success for the work fluctuation relation was achieved in an iontrap setup [29][30][31][32]. Later, this difficult projective measurement scheme was circumvented and an ancilla based Ramsey intereferometric approach was proposed [23] following which the work fluctuation relation was verified [24,25]. Further successful attempts were also made recently to study similar fluctuation relation for open systems [32].In this work, we attempt to verify the quantum version of Jarzynski and Wöjcik heat "exchange fluctuation theorem " (XFT) [7] which has not been achieved till date and this is the gap we want to fill in this work. We employ here a similar interferometric approach, as proposed for measuring work statistics, in a liquid Nuclear Magnetic Resonance ...

Quantum entanglement is a form of correlation between quantum particles that cannot be increased via local operations and classical communication. It has therefore been proposed that an increment of quantum entanglement between probes that are interacting solely via a mediator implies non-classicality of the mediator. Indeed, under certain assumptions regarding the initial state, entanglement gain between the probes indicates quantum coherence in the mediator. Going beyond such assumptions, there exist other initial states which produce entanglement between the probes via only local interactions with a classical mediator. In this process the initial entanglement between any probe and the rest of the system "flows through" the classical mediator and gets localised between the probes. Here we theoretically characterise maximal entanglement gain via classical mediator and experimentally demonstrate, using liquid-state NMR spectroscopy, the optimal growth of quantum correlations between two nuclear spin qubits interacting through a mediator qubit in a classical state. We additionally monitor, i.e., dephase, the mediator in order to emphasise its classical character. Our results indicate the necessity of verifying features of the initial state if entanglement gain between the probes is used as a figure of merit for witnessing non-classical mediator. Such methods were proposed to have exemplary applications in quantum optomechanics, quantum biology and quantum gravity.

Effective Hamiltonians and effective electroweak operators are calculated with the Okubo-Lee-Suzuki formalism for two-nucleon systems. Working within a harmonic oscillator basis, first without and then with a confining harmonic oscillator trap, we demonstrate the effects of renormalization on observables calculated for truncated basis spaces. We illustrate the renormalization effects for the root-mean-square point-proton radius, electric quadrupole moment, magnetic dipole moment, Gamow-Teller transition and neutrinoless double-beta decay operator using nucleon-nucleon interactions from chiral Effective Field Theory. Renormalization effects tend to be larger in the weaker traps and smaller basis spaces suggesting applications to heavier nuclei with transitions dominated by weakly-bound nucleons would be subject to more significant renormalization effects within achievable basis spaces. IntroductionPrecision studies of electroweak properties of nuclei have become of great interest to complement major advances underway in experimental nuclear physics. As an example, significant experimental and theoretical efforts are aimed at searches for neutrinoless double-beta (0ν2β) decay which require significant investments in new experimental facilities and in theoretical advances. Our limited goal here is to use solvable two-nucleon systems within a configuration-interaction (CI) approach in order to explore the dependence of electroweak operators on the CI basis-space truncation when evaluating nuclear properties. Information on the size of these effects can help interpret previous studies and guide plans for calculations in larger nuclei.We select systems of two nucleons interacting via realistic nucleon-nucleon (N N ) interactions both in free space and in a harmonic oscillator (HO) trap for investigating renormalization effects on a suite of electroweak properties. These systems are numerically solvable in a large HO basis space providing high precision results for comparison with approximate results. This allows us to map out the effects arising from the correlations governed by different interactions, as well as the effects due to basis space truncation and the effects linked with the length scale of the environment, the trap. To accurately calculate these 1 arXiv:1809.00276v1 [nucl-th]

Quantum processors are potentially superior to their classical counterparts for many computational tasks including factorization. Circuit methods as well as adiabatic methods have already been proposed and implemented for finding the factors of a given composite number. The main challenge in scaling it to larger numbers is the unavailability of large number of qubits. Here we propose a hybrid scheme that involves both classical and quantum computation, which reduces the number of qubits required for factorization. The classical part involves setting up and partially simplifying a set of bit-wise factoring equations and the quantum part involves solving these coupled equations using a quantum adiabatic process. We demonstrate the hybrid scheme by factoring 551 using a three qubit NMR quantum register.

Sparse matrix-vector multiplication (SpMV) is a critical building block for iterative graph analytics algorithms. Typically, such algorithms have a varying active vertex set across iterations. This variablity has been used to improve performance by either dynamically switching algorithms between iterations (software) or designing custom accelerators (hardware) for graph analytics algorithms. In this work, we propose a novel framework, CoSPARSE, that employs hardware and software reconfiguration as a synergistic solution to accelerate SpMV-based graph analytics algorithms. Building on previously proposed general-purpose reconfigurable hardware, we implement CoSPARSE as a software layer, abstracting the hardware as a specialized SpMV accelerator. CoSPARSE dynamically selects software and hardware configurations for each iteration and achieves a maximum speedup of 2.0× compared to the naïve implementation with no reconfiguration. Across a suite of graph algorithms, CoSPARSE outperforms a state-of-the-art shared memory framework, Ligra, on a Xeon CPU with up to 3.51× better performance and 877× better energy efficiency.