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1
Content available remote

Logic Operations of Charge Qubit in a Triple Quantum Dot

100%
Ptaszyński K., Bułka B.
Acta Physica Polonica A
|
2016
|
vol. 129
|
issue 1a
A-30-A-32
EN
Studies for a single charge qubit and two capacitively coupled qubits built on triple quantum dots are presented. We show feasibility of implementing two-qubit gate operations, e.g. the CPHASE gate can be implemented with the fidelity higher than 99% for strong couplings.
2
Content available remote

Some Examples of Post-Measurement Nonlocal Gates

100%
Song D.
Acta Physica Polonica A
|
2012
|
vol. 121
|
issue 3
589-591
EN
Several proposed quantum computer models include measurement processes, in order to implement nonlocal gates and create necessary entanglement resources during the computation. We discuss some examples in which the measurements can be delayed for two- and three-qubit nonlocal gates. We also discuss implementing arbitrary nonlocal gates when measurements are included during the process.
3
Content available remote

Singlet-Triplet Dephasing in Asymmetric Quantum Dot Molecules

80%
Marcinowski Ł., Roszak K., Machnikowski P.
Acta Physica Polonica A
|
2009
|
vol. 116
|
issue 5
874-876
EN
We discuss pure dephasing of singlet-triplet superpositions in two-electron double quantum dots due to elastic phonon scattering. We generalize our previous results to a system built of two non-identical dots. We show that the asymmetry must be very strong in order to considerably affect the dephasing rate.
4
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Phonon-Induced Pure Dephasing of Two-Electron Spin States in Vertical Quantum Dot Molecules

80%
Roszak K., Machnikowski P.
Acta Physica Polonica A
|
2009
|
vol. 116
|
issue 5
877-878
EN
Phonon-induced dephasing of two-electron spin states in two vertically stacked self-assembled GaAs/InGaAs quantum dots is studied. A pure dephasing process due to elastic phonon scattering is found to dominate at low temperatures. This process is independent of the spin-orbit coupling and does not require the presence of a magnetic field. It relies on interdot tunneling and the Pauli principle, which make the double quantum dot gate for spin based quantum computing possible, and therefore cannot be avoided.
5
Publication available in full text mode
Content available

Quantum Information Processing Using Electron Spins in Quantum Dots

80%
Burkard G., Loss D.
Acta Physica Polonica A
|
2001
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vol. 100
|
issue 2
109-127
EN
We review the theoretical proposal for quantum computing with electron spins in quantum confined structures and discuss the essential requirements for its implementation. The quantum bit is represented by the spin of the electron, as opposed to the charge (orbital) degrees of freedom. In this context, we analyze a number of physical realizations of the elementary building blocks for quantum computation: a universal set of quantum gates, state preparation and measurement. Finally, we discuss the production, transport, and detection of electronic Einstein-Podolski-Rosen pairs, which are an important resource for quantum communication.
6
Publication available in full text mode
Content available

Bose-Einstein Condensates in Optical Lattices

80%
Wasilewski W., Trippenbach M., Rzążewski K.
Acta Physica Polonica A
|
2002
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vol. 101
|
issue 1
47-60
EN
We study an ultracold dilute gas of bosonic atoms in an optical lattice induced by intersecting laser beams. As a first approximation we neglect confining potential and atom-atom interactions. In this case the Gross-Pitaevskij equation reduces to simple Mathieu equation. Upon choosing periodic boundary conditions this problem has well known periodic solution. This simple picture allows to demonstrate localization of the wave packet and formation of the band structure. We calculate spectrum of the excited states as a function of the strength of modulating potential and using a standard adiabaticity criterion we predict the most efficient way to ramp up optical lattice, without higher state excitation. Finally, we discuss the influence of the atom-atom interaction (nonlinearity) on the adiabaticity of the process.
7
Content available remote

Single Electron Spin Operations Employed for Logical Gates of Quantum Computer

80%
Bednarek S., Dudek R.
Acta Physica Polonica A
|
2009
|
vol. 116
|
issue S
S-7-S-12
EN
Electron localized in a quantum dot in the vicinity of conductor surface, causes an induced potential to appear. This potential enables self-focusing of electron wave function. Because of this feature, in a planar nanostructure consisting of a quantum well covered with a layer of an insulator, on top of which metal electrodes are deposited, formation of induced dots and quantum wires is possible. By applying appropriate voltages to the electrodes, it is feasible to transport an electron in a fully controllable way in a form of a stable wave packet between two specific locations in a nanodevice. While transporting an electron along properly shaped closed loops, spin-orbit coupling intrinsically present in a semiconductor nanostructure can be employed to perform operations on an electron spin.
8
Content available remote

System Size Dependence of Entanglement in Quantum One-Dimensional Models

80%
Jakubczyk D., Jakubczyk P.
|
EN
We show that entanglement in one-dimensional spin and electron systems, with one excitation, depends only on the system size and has very simple form in both multipartite and bipartite case. Regarding the multipartite case, we present very simple expressions for global entanglement and N-concurrence, and show that they are mutually related. In the bipartite case, we give expressions for I-concurrence and negativity, and show that they are also dependent on each other.
9
Content available remote

Two-Dimensional Ising Model with Competing Interactions as a Model for Interacting π-Rings

80%
O'Hare A., Kusmartsev F., Kugel K.
|
EN
We investigate the Ising model on a square lattice with antiferromagnetic exchange between nearest and next-nearest neighbors and show that at low temperatures stripe-like and droplet-like superstructures appear. We show that the competing interactions introduce a strong frustration that could plausibly describe the systems with dipole-dipole type interactions and pay particular attention to arrays of interacting Josephson π-rings.
10
Content available remote

Nanodevice for High Precision Readout of Electron Spin

80%
Szumniak P., Bednarek S., Szafran B., Grynkiewicz P.
Acta Physica Polonica A
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2011
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vol. 119
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issue 5
651-653
EN
In this paper we propose and simulate operation of a nanodevice, which enables the electron spin accumulation and very precise read-out of its final value. We exploit the dependence of the electron trajectory on its spin state due to the spin-orbit coupling in order to distinguish between different spin orientations.
11
Publication available in full text mode
Content available

Complete and Partial Loss of Entanglement Due to a Phonon-Assisted Dephasing Process

80%
Roszak K., Machnikowski P., Jacak L.
Acta Physica Polonica A
|
2006
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vol. 110
|
issue 3
331-336
EN
We study the evolution of entanglement between two excitons in a double quantum dot system coupled to a super-Ohmic reservoir. As expected entanglement is more fragile than local coherence, but, surprisingly, for a set of pure states disentanglement can be complete in a finite time under conditions that lead to the usual partial pure-dephasing.
12
Content available remote

Dynamics of a Charge Qubit Encoded in a Double Quantum Dot

80%
Łuczak J., Bułka B.
Acta Physica Polonica A
|
2018
|
vol. 133
|
issue 3
748-750
EN
We study the short time dynamics of a charge qubit encoded in two coherently coupled quantum dots connected to external electrodes. In the regime of sequential tunneling the waiting time distribution is used to investigate in details statistics of the tunneling events and their correlations. We show that the coherent rotation of the qubit state on the Bloch sphere can be seen in tunneling events when an electron is injected and leave the system. Decoherence, relaxation of the qubit state as well as leakage processes are studied by means of transient currents.
13
Content available remote

Magnetic Pentagonal Ring - Galois Extensions and Crystallography

70%
Labuz M., Lulek T.
Acta Physica Polonica A
|
2017
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vol. 132
|
issue 1
97-99
EN
The Galois symmetry of exact Bethe Ansatz eigenstates for magnetic pentagonal ring is shown to bear a close analogy to some crystallographic constructions. Automorphisms of number field extensions associated with these eigenstates prove to be related to choices of the Bravais cells in the finite crystal lattice ℤ₂×ℤ₂, responsible for extension of the cyclotomic field by the Bethe parameters.
14
Content available remote

Collective Luminescence and Phonon-Induced Processes in Double Quantum Dots

70%
Machnikowski P., Roszak K., Sitek A.
Acta Physica Polonica A
|
2009
|
vol. 116
|
issue 5
818-825
EN
We study the evolution of a quantum state of a double quantum dot system interacting with the electromagnetic environment and with the lattice modes, in the presence of a coupling between the two dots. We propose a unified approach to the simulation of the system evolution under joint impact of the two reservoirs. We discuss the sub- and superradiant radiative decay of the system, the phonon-induced decay of entanglement between the dots, and the transfer of excitation between them.
15
Content available remote

Some New Approaches of the XXX Heisenberg Model of the Two-Magnon Sector

70%
Łabuz M., Milewski J., Lulek T.
Acta Physica Polonica A
|
2018
|
vol. 133
|
issue 3
444-446
EN
XXX Heisenberg s-1/2 model has been examined in detail during last decades, however, recently one may find some new insights into that issue. Among several approaches describing the eigenproblem for the finite case, a close look into the structure of Bethe equations (BE) for the two-magnon sector case seems to be particularly interesting. BE enable us to evaluate parameters labeling eigenstates of a magnet, however to find appropriate sets of winding numbers, which parametrize BE, one has to apply the Inverse Bethe Ansatz method. On the other hand, one may choose a different - combinatoric approach - which also parametrizes Bethe eigenstates, with the use of rigging numbers describing string configurations. We present an idea of comparison of the concepts mentioned above for the particular case of two-spin deviations sector.
16
Content available remote

Point Group Interpretation of Galois Symmetry of Bethe Ansatz Solutions of Magnetic Pentagonal Ring

70%
Lulek B., Lulek T., Łabuz M., Milewski J.
Acta Physica Polonica A
|
2015
|
vol. 127
|
issue 2
336-338
EN
Exact solutions of the eigenproblem of the magnetic pentagonal ring exhibit the arithmetic symmetry expressed in terms of a Galois group of a finite extension of the prime field Q of rationals. We propose here a geometric interpretation of this symmetry in the interior of the Brillouin zone, in terms of point groups. Explicitly, it is a subgroup of the direct product C₄ × D₄. We present also the appropriate irreducible representations of the group.
17
Content available remote

Multi-mode ground state interaction terms in C60-based electron donor-acceptor complexes

41%
Sheka E.
Open Physics
|
2004
|
vol. 2
|
issue 2
300-328
EN
Quantum-chemical testing of donor-acceptor properties of binary molecular complexes, related to the singlet state, is suggested as QCh calculations of studied systems and their constituents by using both spin-nondependent (RHF) and spindependent (UHF) versions of the exploited computational tool. The avoided crossing of intermolecular interaction terms of neutral moleculesE int(A 0 B 0) and molecular ionsE int(A + B −) causes a multi-mode character of the ground state term. The dependence of D-A complex properties on the type of the term, space positions of the term minimum, and the interrelation of the corresponding energies are discussed. The suggested approach has been applied to binary complexes C60+X (X=TAE, TDAE, DMMA, COANP, 2Li, Mg).
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