Spin Polarization-Scaling Quantum Maps and Channels

Filippov, S.; Magadov, Kamil Yu.

doi:10.1134/s1995080218010109

Cited by 4 publications

(3 citation statements)

References 34 publications

(40 reference statements)

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“…Finally, the multiple photon addition and subtraction operations can be treated in the same way because Interestingly, in contrast to the quantum channels [32][33][34][35], the quantum informational properties of quantum operations such as capacities and entanglement degradation remain essentially unstudied. From this viewpoint, the fair quantum operations (4) and (5) can be analyzed as paradigmatic examples of operations on continuousvariable quantum states.…”

Section: Discussionmentioning

confidence: 99%

On Quantum Operations of Photon Subtraction and Photon Addition

Filippov

2019

Lobachevskii J Math

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The conventional photon subtraction and photon addition transformations, ̺ → ta̺a † and ̺ → ta † ̺a, are not valid quantum operations for any constant t > 0 since these transformations are not trace nonincreasing. For a fixed density operator ̺ there exist fair quantum operations, N− and N+, whose conditional output states approximate the normalized outputs of former transformations with an arbitrary accuracy. However, the uniform convergence for some classes of density operators ̺ has remained essentially unknown. Here we show that, in the case of photon addition operation, the uniform convergence takes place for the energy-second-moment-constrained states such that tr[̺H 2 ] ≤ E2 < ∞, H = a † a. In the case of photon subtraction, the uniform convergence takes place for the energy-second-moment-constrained states with nonvanishing energy, i.e., the states ̺ such that tr[̺H] ≥ E1 > 0 and tr[̺H 2 ] ≤ E2 < ∞. We prove that these conditions cannot be relaxed and generalize the results to the cases of multiple photon subtraction and addition.

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Section: Discussionmentioning

confidence: 99%

On Quantum Operations of Photon Subtraction and Photon Addition

Filippov

2019

Lobachevskii J Math

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“…Moreover, the interface repulsion interactions of metal-Mg or metal-O were more vigorous than those of Al-Mg or Al-O. In the TiCo-Mg and TiCo-O terminations, the bond lengths of Co-Mg and Co-O were longer than those of Ti-Mg and Ti-O, thereby creating an uneven interface atomic layer that led to further spin electronic scattering from the mechanical mismatch interface layers to weaken the spin polarization [37]. Table 2 summarizes the atom-resolved magnetic moments (AMMs) at the interface and subinterface layers in Ti 2 CoAl and at the interface layer in MgO for various terminations of the Ti 2 CoAl/MgO(100) interface.…”

Section: Interface Structuresmentioning

confidence: 99%

Structure, Magnetism, and Electronic Properties of Inverse Heusler Alloy Ti2CoAl/MgO(100) Herterojuction: The Role of Interfaces

Huang

Zhou

et al. 2018

Applied Sciences

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In this study, the interface structures, atom-resolved magnetism, density of states, and spin polarization of 10 possible atomic terminations in the Ti 2 CoAl/MgO(100) heterojunction were comprehensively investigated using first-principle calculations. In the equilibrium interface structures, the length of the alloy-Mg bond was found to be much longer than that of the alloy-O bond because of the forceful repulsion interactions between the Heusler interface atoms and Mg atoms. The competition among d-electronic hybridization, d-electronic localization, and the moving effect of the interface metal atoms played an important role in the interface atomic magnetic moment. Unexpected interface states appeared in the half-metallic gap for all terminations. The "ideal" half-metallicity observed in the bulk had been destroyed. In TiAl-Mg and AlAl-O terminations, the maximal spin polarization of about 65% could be reserved. The tunnel magnetoresistance (TMR) value was deduced to be lower than 150% in the Ti 2 CoAl/MgO(100) heterojunction at low temperature.

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“…1 , Corollary 6.13), and is trace preserving as 3 k=1 J 2 k = j(j + 1)I (Ref. 3 , section 6.1.2, formula (5)). The latter formula is also responsible for unitality of the map (1).…”

Section: Introductionmentioning

confidence: 99%

Quantum informational properties of the Landau–Streater channel

Filippov

Kuzhamuratova

2019

Journal of Mathematical Physics

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We study the Landau-Streater quantum channel Φ : B(H d ) → B(H d ), whose Kraus operators are proportional to the irreducible unitary representation of SU (2) generators of dimension d. We establish SU (2) covariance for all d and U (3) covariance for d = 3. Using the theory of angular momentum, we explicitly find the spectrum and the minimal output entropy of Φ. Negative eigenvalues in the spectrum of Φ indicate that the channel cannot be obtained as a result of Hermitian Markovian quantum dynamics. Degradability and antidegradability of the Landau-Streater channel is fully analyzed. We calculate classical and entanglement-assisted capacities of Φ. Quantum capacity of Φ vanishes if d = 2, 3 and is strictly positive if d 4. We show that the channel Φ ⊗ Φ does not annihilate entanglement and preserves entanglement of some states with Schmidt rank 2 if d 3.

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Spin Polarization-Scaling Quantum Maps and Channels

Cited by 4 publications

References 34 publications

On Quantum Operations of Photon Subtraction and Photon Addition

On Quantum Operations of Photon Subtraction and Photon Addition

Structure, Magnetism, and Electronic Properties of Inverse Heusler Alloy Ti2CoAl/MgO(100) Herterojuction: The Role of Interfaces

Quantum informational properties of the Landau–Streater channel

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