Implementing quantum gates through scattering between a static and a flying qubit

Cordourier-Maruri, Guillermo; Ciccarello, Francesco; Omar, Yasser; Zarcone, M.; Coss, Romeo de; Bose, Sougato

doi:10.1103/physreva.82.052313

Cited by 32 publications

(33 citation statements)

References 34 publications

(82 reference statements)

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“…are the projector operators associated with the singlet and triplet subspaces, respectively, of the f -SQ 1 system. Note that in the computational basis {|α f α 1 } (α f , α 1 =↑, ↓), a matrix element α f α 1 |R f 1 |α f α 1 yields the probability amplitude that, given the initial joint spin state |α f α 1 , f is reflected back and the final spin state is |α f α 1 [8,9] (an analogous statement holds forT f 1 ). Via the identities (4) and (5), one can easily verify that equation (7) immediately entails the proper normalization condition…”

Section: Read-out Of a Single Static Memory Qubitmentioning

confidence: 98%

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Selective writing and read-out of a register of static qubits

et al. 2013

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We propose a setup comprising an arbitrarily large array of static qubits (SQs), which interact with a flying qubit (FQ). The SQs work as a quantum register, which can be written or read out by means of the FQ through quantum state transfer (QST). The entire system, including the FQ's motional degrees of freedom, behaves quantum mechanically. We demonstrate a strategy allowing for selective QST between the FQ and a single SQ chosen from the register. This is achieved through a perfect mirror located beyond the SQs and suitable modulation of the inter-SQ distances.A prominent paradigm in quantum information processing (QIP) [1] is to employ flying qubits (FQs) and static qubits (SQs) as the carriers and registers of quantum information, respectively [2]. Key to such an idea is the ability to write and read out the information content of a SQ by means of a FQ. By this, here we mean that an efficient quantum state transfer (QST) between these two types of qubits must be possible on demand. In this picture, control over memory allocation appears to be a desirable if not indispensable requirement. For instance, one can envisage the situation where only one or a few SQs are available, e.g. because the remaining ones are encoding some information to save. On the other hand, one may need to carry away only the information saved in certain specific SQs. Alternatively, only a restricted area of the register of SQs may be interfaced with some external processing network where one would like to eventually convey information or from which output data are to be received. In such cases, the ability of selecting the exact location where the information content of the FQ should be uploaded or downloaded is demanded. Ideally, according to the schematics in figure 1, one would like the FQ to reach the specific target SQ, then fully transfer its quantum state to this and eventually fly away. Evidently, this picture is implicitly based on the assumption that, firstly, the motional degrees of freedom (MDOFs) of the FQ are in fact fully classical and, secondly, these can be accurately controlled. Despite its simplicity, although interesting research along these lines is being carried out mostly through the so-called surface acoustic waves (see e.g. [3] and references therein), such an approach calls for a very high level of control.If set within a fully quantum framework, the most natural situation to envisage is the one where the FQ, besides bearing an internal spin, moves in a quantum mechanical way and hence propagates as a wave-like object. Such a circumstance substantially complicates the dynamics in that, besides the complex spin-spin interactions, intricate wave-like effects such as multiple reflections between the many SQs occur as well. This appears to be an adverse environment to accomplish selective QST: while ideally one would like to focus the FQ's wave packet right on the target SQ, the former is expected to spread throughout the SQs' register. Thus, not only is it non-trivial what strategy would enable selective QST but ...

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Section: Read-out Of a Single Static Memory Qubitmentioning

confidence: 98%

“…Thereby, off-diagonal entries r 01 must vanish, which yields the condition r (m) s = e −2ikd 2 , i.e. kd 2 = π − arg[r (m) s (g)]/2 = h(kd 1 ), according to our definition of the h function (see above) 8 . By replacing this into equations (19) and (20), we immediately end up with r 00 = −r 11 = 1.…”

Section: Two Static Qubitsmentioning

confidence: 99%

Selective writing and read-out of a register of static qubits

et al. 2013

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“…In general, this proposal has shown that electron scattering based QIPs have a remarkable resilience, and they require a low level control over the spin interaction [19].…”

Section: Introductionmentioning

confidence: 99%

“…On the other hand, the involvement of the spatial degrees of freedom is a disadvantage of using electron scattering as an interaction channel between spins because it makes the scattering a non-unitary operation [19,28]. In order to create a unitary process, we need to implement a post-selection protocol, such as a spin polarization detection, and the possible implementations will be non-deterministic.…”

Section: Introductionmentioning

confidence: 99%

Entanglement of magnetic impurities through electron scattering in an electric field

Lazo-Arjona

Cordourier-Maruri

Coss

2015

Quantum Inf Process

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“…It has been used to study the conduction properties of crystals through the Kronig-Penney model [22] and Anderson localization in a disordered impurity array [23,24,25,26]. In a solid state quantum information scenario, δ-function potential barriers are used to depict the instantaneous interaction between a flying spin and a fixed magnetic impurity [27,28,29,30,31,32], to implement teleportation [33] and quantum memory [34].…”

Section: Introductionmentioning

confidence: 99%

Recurrence in Resonant Transmission of One-Dimensional Array of Delta Potentials

2014

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The resonant transmission of a moving particle which interacts with an one-dimensional array of N δ-function potentials is investigated. A suitable transfer matrix formulation is used to obtain the particle transmission. We give the parameters for perfect tunnelling and the transcendental equation for the quasi-bound state energies for N = 2, 3 and 4. Conditions for perfect tunnelling and resonant transmission are discussed for arrays with arbitrary N . A model to explain how the tunnelling energy filter works in these systems is proposed here.

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Implementing quantum gates through scattering between a static and a flying qubit

Cited by 32 publications

References 34 publications

Selective writing and read-out of a register of static qubits

Selective writing and read-out of a register of static qubits

Entanglement of magnetic impurities through electron scattering in an electric field

Recurrence in Resonant Transmission of One-Dimensional Array of Delta Potentials

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