Generalized parity measurements

Ionicioiu, Radu; Popescu, A.; Munro, William J.; Spiller, Timothy P.

doi:10.1103/physreva.78.052326

Cited by 29 publications

(25 citation statements)

References 41 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We develop a full ancilla-mediated model of quantum computation based only on controlled displacement operators acting on an ancilla qudit. The previous work [30,31] on ancillary qudits can also be understood within this framework and we show that the computational advantages demonstrated in the qubus model can be transferred into this finite dimensional context.…”

Section: Introductionmentioning

confidence: 77%

“…As this is a two-qubit entangling gate as long as xp = nd for any integer n this is universal for quantum computation on the register with the addition of single-qubit gates on the register. It has already been shown that there are computational advantages that can be gained from using ancillary qudits to aid a computational model [27,30,31]. We consider the generalized Toffoli gate which maps the basis states of n control and one target qubit to |q 1 ,q 2 .…”

Section: B the Computational Modelmentioning

confidence: 99%

“…Models that utilize qudits have been shown to exhibit a reduction in the number of operations required to implement a Toffoli gate [27][28][29]. In particular, it has been shown that using a qudit ancilla can aid a computational model, with advantages including large savings in the number of operations required to implement a generalized Toffoli gate (a unitary controlled on multiple qubits) [30] and simple methods for realizing generalized parity measurements on a register of qubits [31]. These results are not directly applicable to the qubus model, however, we show, using the formalism for the finite lattice phase space of a qudit [32,33], that the computational advantages of a field-mode bus also apply in the case of a qudit ancilla.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Quantum computation mediated by ancillary qudits and spin coherent states

2015

View full text Add to dashboard Cite

Publisher's copyright statement:Reprinted with permission from the American Physical Society: Physical Review A 91, 012308 c (2015) by the American Physical Society. Readers may view, browse, and/or download material for temporary copying purposes only, provided these uses are for noncommercial personal purposes. Except as provided by law, this material may not be further reproduced, distributed, transmitted, modied, adapted, performed, displayed, published, or sold in whole or part, without prior written permission from the American Physical Society.Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. Models of universal quantum computation in which the required interactions between register (computational) qubits are mediated by some ancillary system are highly relevant to experimental realizations of a quantum computer. We introduce such a universal model that employs a d-dimensional ancillary qudit. The ancilla-register interactions take the form of controlled displacements operators, with a displacement operator defined on the periodic and discrete lattice phase space of a qudit. We show that these interactions can implement controlled phase gates on the register by utilizing geometric phases that are created when closed loops are traversed in this phase space. The extra degrees of freedom of the ancilla can be harnessed to reduce the number of operations required for certain gate sequences. In particular, we see that the computational advantages of the quantum bus (qubus) architecture, which employs a field-mode ancilla, are also applicable to this model. We then explore an alternative ancilla-mediated model which employs a spin ensemble as the ancillary system and again the interactions with the register qubits are via controlled displacement operators, with a displacement operator defined on the Bloch sphere phase space of the spin coherent states of the ensemble. We discuss the computational advantages of this model and its relationship with the qubus architecture.

show abstract

Section: Introductionmentioning

confidence: 77%

Section: B the Computational Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Quantum computation mediated by ancillary qudits and spin coherent states

2015

View full text Add to dashboard Cite

show abstract

“…The largest diversity of multipartite entangled states has been achieved so far by using the polarization degrees of freedom of photons, generated by spontaneous parametric down-conversion (SPDC) and subsequently fed into special arrangements of linear optical elements [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25]. Although a large variety of different states can be produced by this technique, it usually suffers from the need of a particular experimental configuration for the generation of a particular entangled state [9][10][11][12][13][14][15][16][17][18].…”

Section: Introductionmentioning

confidence: 99%

Versatile source of polarization-entangled photons

et al. 2010

View full text Add to dashboard Cite

We propose a method for the generation of a large variety of entangled states, encoded in the polarization degrees of freedom of N photons, within the same experimental setup. Starting with uncorrelated photons, emitted from N arbitrary single-photon sources, and using linear optical tools only, we demonstrate the creation of all symmetric states (e.g., GHZ and W states), as well as all symmetric and nonsymmetric total angular momentum eigenstates of the N-qubit compound.

show abstract

“…It has been shown that parity meters provide a new realization of quantum computing [30,31] and are capable of building up many different types of entangled states [22,23,32]. Parity meters have also been recently been used to explore rapid two-party purification and enhanced entanglement generation using feedback control [33].…”

Section: Even Paritymentioning

confidence: 99%

Entanglement genesis under continuous parity measurement

Williams

Jordan

2008

Phys. Rev. A

View full text Add to dashboard Cite

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/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 insights on the optimization of entanglement generation by measurement.PACS numbers: 03.65. Ta,03.65.Yz Entanglement is arguably the most fascinating aspect of quantum mechanics and plays a central role in quantum information science. The peculiar non-classical correlations which entanglement characterizes are the basis for exciting applications such as teleportation, quantum encryption, and many others [1]. Since the concept of entanglement appeared, there has been much research into its properties. One aspect of this research has been how to quantify the amount of entanglement contained in a quantum state. Many different entanglement measures have been introduced with varying degrees of success [2]. In the two qubit case, the concurrence measure of entanglement can be explicitly given in general for any mixed state [3], making this system ideal for further research.In parallel with these measures, investigations into the dynamics of entanglement began and continue still. If entanglement is to be used as a resource, then its dynamical evolution must be understood. Of particular interest is how entanglement decays when the entangled systems are coupled to the environment. It was found that entanglement typically decreases at an exponential rate, faster than single-qubit decoherence [4,5,6,7]. An important step was the realization by Jakóbczyk [8] and Yu and Eberly [9] that entanglement can reach zero in a finite time. This behavior was dubbed "entanglement sudden death" [9,10,11,12,13,14,15] and has received much recent attention. The ability of entanglement to have this non-analytic behavior can be traced back to its definition: two particles are considered entangled if their combined density matrix cannot be decomposed into a weighted sum of pure, separable density matrices. If such a decomposition can be found, then it is defined to be seperable, having zero entanglement. While it is important to understand the disappearance of entanglement, we must also understand how it is generated in the first place. This is the topic d...

show abstract

Generalized parity measurements

Cited by 29 publications

References 41 publications

Quantum computation mediated by ancillary qudits and spin coherent states

Quantum computation mediated by ancillary qudits and spin coherent states

Versatile source of polarization-entangled photons

Entanglement genesis under continuous parity measurement

Contact Info

Product

Resources

About