Parity Measurements Research Articles

Competition at the feed bunk changes the feeding, standing, and social behavior of transition dairy cows

Transition dairy cows are vulnerable to the negative consequences of depressed feed intake around calving. Competition can decrease feeding activity in midlactation cows, but the effects of competition on the transition cow are not well understood. The objective was to test the effect of competition on the behavior and feed intake of transition cows. Standing behavior, feeding behavior, and dry matter intake were monitored from 1 wk before to 2 wk after calving for 36 Holstein dairy cows. Displacements at the feed bins were recorded the week before calving. Cows were assigned to either competitive (2:1 cows:feed bin) or noncompetitive (1:1 cow:feed bin) treatments. Treatment groups were balanced for parity and baseline feeding measures, resulting in 8 primiparous and 10 multiparous cows per treatment. Competition increased the number of displacements at the feed bins for both primiparous and multiparous cows. Primiparous cows had no change in feed intake or standing time when fed in a competitive environment, but did increase the time spent for each meal during the week before calving (28 ± 1.5 vs. 24 ± 1.5 min/meal). In the week before and after calving, competitively fed multiparous cows had a lower feeding time per visit than noncompetitively fed cows (4.2 ± 0.5 vs. 5.8 ± 0.5 kg/visit and 5.3 ± 0.7 vs. 7.0 ± 0.7 kg/visit, respectively). Multiparous cows ate at a faster rate 2 wk after calving (142 ± 11 vs. 105 ± 11 g/min). Multiparous cows in the competitive treatment increased the time they spent standing (without eating) during the week after calving compared with cows in the noncompetitive treatment (820 ± 44 vs. 649 ± 44 min/d). Feeding rate was correlated with a displacement index in multiparous cows, whereby cows with lower displacement indices ate more rapidly. Results indicate that restricting access to feed increases displacements regardless of parity, and alters the feeding and standing behavior of primiparous and multiparous cows differently.

Experimental measurement of lower and upper bounds of concurrence for mixed quantum states

We experimentally measure the lower and upper bounds of concurrence for a set of two-qubit mixed quantum states using photonic systems. The measured concurrence bounds are in agreement with the results evaluated from the density matrices reconstructed through quantum state tomography. In our experiment, we propose and demonstrate a simple method for providing two faithful copies of a two-photon mixed state required for parity measurements: two photon pairs generated by two neighboring pump-laser pulses through optical parametric down-conversion processes represent two identical copies. This method can be conveniently generalized for entanglement estimation of multiphoton mixed states.

Direct probing of the Wigner function by time-multiplexed detection of photon statistics

We investigate the capabilities of loss-tolerant quantum state characterization using a photon-number resolving, time-multiplexed detector (TMD). We employ the idea of probing the Wigner function point-by-point in phase space via photon parity measurements and displacement operations, replacing the conventional homodyne tomography. Our emphasis lies on reconstructing the Wigner function of non-Gaussian Fock states with highly negative values in a scheme that is based on a realistic experimental set-up. In order to establish the concept of loss-tolerance for state characterization, we show how losses can be decoupled from the impact of other experimental imperfections, i.e. the non-unity transmittance of the displacement beamsplitter and non-ideal mode overlap. We relate the experimentally accessible parameters to effective ones that are needed for an optimized state reconstruction. The feasibility of our approach is tested by Monte Carlo simulations, which provide bounds resulting from statistical errors that are due to limited data sets. Our results clearly show that high losses can be accepted for a defined parameter range, and moreover, that—in contrast to homodyne detection—mode mismatch results in a distinct signature, which can be evaluated by analysing the photon number oscillations of the displaced Fock states.

Physical model of continuous two-qubit parity measurement in a cavity-QED network

We propose and analyze a physical implementation of two-qubit parity measurements as required for continuous error correction, assuming a setup in which the individual qubits are strongly coupled to separate optical cavities. A single optical probe beam scatters sequentially from the two cavities, and the continuous parity measurement is realized via fixed quadrature homodyne photodetection. We present models based on quantum stochastic differential equations (QSDEs) for both an ideal continuous parity measurement and our proposed cavity quantum electrodynamics (cavity QED) implementation; a recent adiabatic elimination theorem for QSDEs is used to assert strong convergence of the latter to the former in an appropriate limit of physical parameters. Performance of the cavity QED scheme is studied via numerical simulation with experimentally realistic parameters.

Manipulating the quantum information of the radial modes of trapped ions: linear phononics, entanglement generation, quantum state transmission and non-locality tests

We present a detailed study on the possibility of manipulating quantum information encoded in the ‘radial’ modes of arrays of trapped ions (i.e. in the ions' oscillations orthogonal to the trap's main axis). In such systems, because of the tightness of transverse confinement, the radial modes pertaining to different ions can be addressed individually. In the first part of the paper we show that, if local control of the radial trapping frequencies is available, any linear optical and squeezing operation on the locally defined modes—on single as well as on many modes—can be reproduced by manipulating the frequencies. Then, we proceed to describe schemes apt to generate unprecedented degrees of bipartite and multipartite continuous variable (CV) entanglement under realistic noisy working conditions and even restricting only to a global control of the trapping frequencies. Furthermore, we consider the transmission of the quantum information encoded in the radial modes along the array of ions, and show it to be possible to a remarkable degree of accuracy, for both finite-dimensional and CV quantum states. Finally, as an application, we show that the states which can be generated in this setting allow for the violation of multipartite non-locality tests, by feasible displaced parity measurements. Such a demonstration would be a first test of quantum non-locality for ‘massive’ degrees of freedom (i.e. for degrees of freedom describing the motion of massive particles).

Mental health parity.

Probably the most far-reaching legislation that affects nurse therapists today is that of mental health parity. Officially designated Decade of the Brain, the 1990s brought unprecedented federal and state legislation to end health insurance discrimination against individuals with mental illnesses. Federal Parity Mental Health Parity Act of 1996. The Mental Health Parity Act of 1996 became effective January 1, 1997, and will sunset on September 30, 2001. It requires employers that offer mental health benefits to set annual and lifetime caps equal to those for medical and surgical benefits. The measure excludes businesses with 50 or fewer employees, and allows all employers to be exempted from the law if their costs rise more than 1% as a result of complying with the requirements. The law allows health insurance plans to set different benefit levels for copayments, deductibles, out-of-pocket payments, inpatient hospital days, and outpatient visits. Relationship to state law. A state law requiring more comprehensive coverage is not weakened by the federal parity law, nor does the federal law preclude a state from enacting stronger parity legislation. On April 14, 1999, U.S. Senators Pete Domenici (R-NM) and Paul Wellstone (D-MN) introduced the Mental Health Equitable Treatment Act of 1999, which would require full health insurance parity for the most severe, biologically based mental illnesses. This legislation would prohibit unequal restrictions on annual and lifetime mental health benefits, inpatient hospital days, outpatient visits, and out-of-pocket expenses. Variations and amendments to this federal bill are being considered. Overview of State Parity Laws After the Mental Health Parity Act of 1996 was signed into law, the momentum shifted to the states. A firestorm of legislative activity created a patchwork quilt of various parity laws around the country. A total of 28 states now have some degree of mental health parity, with fairness bills pending in many other state legislatures. Depending on the state, mental health parity may include any combination of the following two items: 1. Equalization of insurance benefits in relation to annual and lifetime caps 2. Equalization of benefit levels for copayments, deductibles, out-of-pocket payments, inpatient hospital days, and outpatient visits. In 1999, 11 states (California, Hawaii, Indiana [expansion of '97 law], Louisiana, Missouri [expansion of '97 law], Montana, Nebraska, Nevada, New Jersey, Oklahoma, Virginia) and two territories (Guam, Puerto Rico) passed parity legislation. In 1998, four states (Delaware, Georgia, South Dakota, Tennessee) passed parity legislation. In 1997, nine states (Arizona, Arkansas, Colorado, Connecticut, Indiana, Missouri [managed care only], South Carolina, Texas [expansion of earlier requirement], Vermont) passed mental illness parity legislation. Between 1991 and 1996, seven states (Maine, Maryland, Minnesota, New Hampshire, North Carolina [state employees only by administrative order], Rhode Island, Texas [state employees only]) effected mental illness parity measures. As each state passes some form of parity legislation or expands existing law, managed care networks are opening up to accept additional therapists to handle the increased workload. The NAMI website gives a state-by-state breakdown of mental illness parity laws. At this site it is possible to find out the specific provisions each state has passed, if any, and when the law has or will become effective. If you reside in a state that has recently passed or amended parity legislation, you are in a window of opportunity that will not last long. Once networks reach their provider quotas, it will be very difficult to gain entry. To take advantage of this window of opportunity, here are several steps you can take: 1. …

Measurement-based approach to entanglement generation in coupled quantum dots

The remarkable phenomenon of measurement-induced quantum entanglement has recently been demonstrated between noninteracting atomic systems [D. L. Moehring et al., Nature (London) 449, 68 (2007)]. In the solid state, the technique may offer a new means of harnessing the strong interactions between neighboring units without the need for precise control over interactions. Recently, we proposed a method for optical parity measurements in a coupled quantum dot system [A. Kolli et al., Phys. Rev. Lett. 97, 250504 (2006)]. Here we perform a comprehensive analytic and numerical study to determine the feasibility of realizing this method using existing technology. We calculate the effects of possible error sources including nonideal photon detectors, ineffective spin-selective excitation, and dot distinguishability (both spatial and spectral). Furthermore, we present an experimental approach for verifying the success of the parity measurement. We conclude that experimental realization of the process should be feasible immediately.

Entanglement genesis under continuous parity measurement

We examine the stochastic dynamics of entanglement for an uncoupled two-qubit system, undergoing continuous parity measurement. Starting with a fully mixed state, the entanglement is zero for a finite amount of time, when it is suddenly created, which we refer to as entanglement genesis. There can be further entanglement sudden death or birth events culminating in the formation of a fully entangled state. We present numerical investigations of this effect together with statistics of the entanglement genesis time in the weak measurement limit as well as the quantum Zeno limit. An analytic treatment of the physics is presented, aided by the derivation of a simple concurrence equation for Bell basis $X$ states. The probability of entanglement border crossing and mean first passage times are calculated for the case of measurement dynamics alone. We find that states with almost the same probability of entanglement border crossing can have very different average crossing times. Our results provide insight on the optimization of entanglement generation by measurement.

Generalized parity measurements

Measurements play an important role in quantum computing (QC), by either providing the nonlinearity required for two-qubit gates (linear optics QC), or by implementing a quantum algorithm using single-qubit measurements on a highly entangled initial state (cluster state QC). Parity measurements can be used as building blocks for preparing arbitrary stabilizer states, and, together with 1-qubit gates are universal for quantum computing. Here we generalize parity gates by using a higher dimensional (qudit) ancilla. This enables us to go beyond the stabilizer/graph state formalism and prepare other types of multi-particle entangled states. The generalized parity module introduced here can prepare in one-shot, heralded by the outcome of the ancilla, a large class of entangled states, including GHZ_n, W_n, Dicke states D_{n,k}, and, more generally, certain sums of Dicke states, like G_n states used in secret sharing. For W_n states it provides an exponential gain compared to linear optics based methods.

Sub-shot-noise quantum optical interferometry: a comparison of entangled state performance within a unified measurement scheme

Phase measurement using a lossless Mach–Zehnder interferometer with certain entangled N-photon states can lead to a phase sensitivity of the order of 1/N, the Heisenberg limit. However, previously considered output measurement schemes are different for different input states to achieve this limit. We show that it is possible to achieve this limit just by the parity measurement for all the commonly proposed entangled states. Based on the parity measurement scheme, the reductions of the phase sensitivity in the presence of photon loss are examined for the various input states.

Parity Victory Was Long, Winding Road

Parity Victory Was Long, Winding Road

One Step to Generate Cluster States Using Dipole-Induced Transparency in a Cavity-Waveguide System

We present a very simple scheme for generating four-qubit cluster states with one step using parity measurement based on dipole-induced transparency in a cavity-waveguide system. The scheme only uses the photon detectors to check the parity of the spatially separated dipole, which are the same (even parity) or different (odd parity) through measuring the light fields in the waveguide. The initial entangled states remain after nondetective identification and they can be used for successive tasks.

Scalable method to estimate experimentally the entanglement of multipartite systems

We present an efficient experimental estimation of the multipartite entanglement of mixed quantum states in terms of simple parity measurements.

Regularized tripartite continuous variable EPR-type states with Wigner functions and CHSH violations

We consider tripartite entangled states for continuous variable systems of EPR type, which generalize the famous bipartite CV EPR states (eigenvectors of conjugate choices X1 − X2, P1 + P2, of the systems' relative position and total momentum variables). We give the regularized forms of such tripartite EPR states in second-quantized formulation, and derive their Wigner functions. This is directly compared with the established NOPA-like states from quantum optics. Whereas the multipartite entangled states of NOPA type have singular Wigner functions in the limit of large squeezing, r → ∞, or tanh r → 1− (approaching the EPR states in the bipartite case), our regularized tripartite EPR states show singular behaviour not only in the approach to the EPR-type region (s → 1 in our notation), but also for an additional, auxiliary regime of the regulator . While the s → 1 limit pertains to tripartite CV states with singular eigenstates of the relative coordinates and remaining squeezed in the total momentum, the limit yields singular eigenstates of the total momentum, but squeezed in the relative coordinates. Regarded as expectation values of displaced parity measurements, the tripartite Wigner functions provide the ingredients for generalized CHSH inequalities. Violations of the tripartite CHSH bound (B3 ⩽ 2) are established, with in the canonical regime (s → 1+), as well as in the auxiliary regime .

Few States Act on Parity Improvements This Year

Few States Act on Parity Improvements This Year

Quantum Nonlocality and Entanglement of Pair Cat States with Phase Decoherence

We investigate the entanglement of pair cat states in the phase damping channel by adopting the log-negativity and then study the possible violations of Bell's inequalities for the pair cat states in terms of the Wigner representation in phase space based upon parity measurement and displacement operation.

Impact of parity on anthropometric measures of obesity controlling by multiple confounders: a cross-sectional study in Chilean women

Aim:To find out whether there is an association between parity and obesity, evaluated through body mass index (BMI), waist circumference (WC), waist-to-hip ratio (WHR) and waist-to-height ratio (WHtR) in Chilean...

Controlled-NOT gate for multiparticle qubits and topological quantum computation based on parity measurements

We discuss a measurement-based implementation of a controlled-NOT (CNOT) quantum gate. Such a gate has recently been discussed for free electron qubits. Here we extend this scheme for qubits encoded in product states of two (or more) spins-1/2 or in equivalent systems. The key to such an extension is to find a feasible qubit-parity meter. We present a general scheme for reducing this qubit-parity meter to a local spin-parity measurement performed on two spins, one from each qubit. Two possible realizations of a multiparticle CNOT gate are further discussed: electron spins in double quantum dots in the singlet-triplet encoding, and nu=5/2 Ising non-Abelian anyons using topological quantum computation braiding operations and nontopological charge measurements.

Strangeness in the nucleon: Newest results from Happex and G0

We present an introduction to accurate measurements of the weak neutral current in the elastic scattering of longitudinally polarized electrons off hadronic targets, and show how they can provide new and stringent limits on the contribution of strange quarks to the nucleon form factors. Such a contribution is of particular interest for the study of nucleon structure, since strange quarks do not contribute to the valence state and give us a direct insight into the dynamics of quark–antiquark fluctuations. We discuss the latest published results of Happex and G0 experiments as well as the perspectives of high precision measurements of parity violating asymmetries.

Physical properties of the Schur complement of local covariance matrices

General properties of global covariance matrices representing bipartite Gaussian states can be decomposed into properties of local covariance matrices and their Schur complements. We demonstrate that given a bipartite Gaussian state ρ12 described by a 4 × 4 covariance matrix V, the Schur complement of a local covariance submatrix V1 of it can be interpreted as a new covariance matrix representing a Gaussian operator of party 1 conditioned to local parity measurements on party 2. The connection with a partial parity measurement over a bipartite quantum state and the determination of the reduced Wigner function is given and an operational process of parity measurement is developed. Generalization of this procedure to an n-partite Gaussian state is given, and it is demonstrated that the n − 1 system state conditioned to a partial parity projection is given by a covariance matrix such that its 2 × 2 block elements are Schur complements of special local matrices.