arXiv subjects

P. Szumniak

Publications and source records attributed to P. Szumniak.

7 recordsLinked to original sources

arXiv2021

Helical and topological phase detection based on nonlocal conductance measurements in a three terminal junction

The helical state is a fundamental prerequisite for many spintronics applications and Majorana zero mode engineering in nanoscopic semiconductors. Its existence in quasi-one-dimensional nanowires was predicted to be detectable as a characteristic reentrant behavior in the conductance, which in a typical two-terminal architecture may be difficult to distinguish from other possible phenomena such as Fabry-Perot oscillations. Here we present an alternative method of helical gap detection free of the mentioned ambiguity, and based on the nonlocal conductance measurements in a three-terminal junction. We find that the interplay between the spin-orbit coupling and the perpendicular magnetic field leads to a spin-dependent trajectory of electrons and as a consequence a preferential injection of electrons in one of the arms. This causes a remarkable enhancement of nonlocal conductance in the helical gap regime. We show that this phenomenon can be also used to detect the topological superconducting phase when the junction is partially proximitized by an s-wave superconductor.

cond-mat.mes-hall↗

arXiv2020

Spin-selective resonant tunneling induced by Rashba spin-orbit interaction in semiconductor nanowire

We consider a single electron confined within a quantum wire in a system of two electrostatically-induced QDs defined by nearby gates. The time-varying electric field, of single GHz frequency, perpendicular to the quantum wire, is used to induce the Rashba coupling and enable spin-dependent resonant tunneling of the electron between two adjacent potential wells with fidelity over 99.5%. This effect can be used for the high fidelity all-electrical electron-spin initialization or readout in the spin-based quantum computer. In contrast to other spin initialization methods, our technique can be performed adiabatically without increase in the energy of the electron. Our simulations are supported by a realistic self-consistent time-dependent Poisson-Schroedinger calculations.

cond-mat.mes-hall↗

arXiv2016

Generation of spin-dependent coherent states in a quantum wire

We propose an all-electrically controlled nanodevice - a gated semiconductor nanowire - capable of generating a coherent state of a single electron trapped in a harmonic oscillator or superposition of such coherent states - the Schr\"odinger cat state. In the proposed scheme, electron in the ground state of the harmonic potential is driven by resonantly oscillating Rashba spin-orbit coupling. This allows for the creation of the Schr\"odinger cat state with superposition amplitudes depending on the initial electron spin state. Such a method can be used for initialization of a single spin qubit defined in a coherent state. The harmonic confinement potential along the InSb nanowire and the modulation of the Rashba spin-orbit coupling is obtained by proper gating. The results are supported by realistic three-dimensional time-dependent self consistent Poisson-Schr\"odinger calculations.

quant-ph↗

arXiv2015

Electron spin rotations induced by oscillating Rashba interaction in a quantum wire

A novel method and nanodevice are introduced that allows to rotate the single electron spin confined in a gated electrostatic InSb nanowire quantum dot. Proposed method does not require application of any (oscillating or static) external magnetic fields. Our proposal instead employs spatial and time modulation of confining potential induced by electric gates, which, in turn leads to oscillating Rashba type spin-orbit coupling. Moving electron back and forth in such a variable Rashba field allows for realization of spin rotations around two different axes separately without using an external magnetic field. The results are supported by realistic three-dimensional time dependent Poisson-Schrödinger calculations for systems and material parameters corresponding to experimentally accessible structures.

cond-mat.mes-hall↗

arXiv2014

Electron spin separation without magnetic field

A nanodevice capable of separating spins of two electrons confined in a quantum dot formed in a gated semiconductor nanowire is proposed. Two electrons confined initially in a single quantum dot in the singlet state are transformed into the system of two electrons confined in two spatially separated quantum dots with opposite spins. In order to separate the electrons' spins we exploit transitions between the singlet and the triplet state which are induced by resonantly oscillating Rashba spin-obit coupling strength. The proposed device is all electrically controlled and the electron spin separation can be realized within tens of picoseconds. The results are supported by solving numerically quasi-one-dimensional time-dependent Schroedinger equation for two electrons, where the electron-electron correlations are taken into account in the exact manner.

cond-mat.mes-hall↗

arXiv2013

All electrically controlled quantum gates for single heavy hole spin qubits

In this paper, several nanodevices which realize basic single heavy hole qubit operations are proposed and supported by time dependent self consistent Poisson-Schrödinger calculations using a four band heavy hole-light hole model. In particular we propose a set of nanodevices which can act as Pauli X, Y, Z quantum gates and as a gate that acts similar as a Hadamard gate (i.e. it creates a balanced superposition of basis states but with an additional phase factor) on the heavy hole spin qubit. We also present the design and simulation of a gated semiconductor nanodevice which can realize an arbitrary sequence of all these proposed single quantum logic gates. The proposed devices exploit the self-focusing effect of the hole wave function which allows for guiding the hole along a given path in the form of a stable soliton-like wave packet. Thanks to the presence of the Dresselhaus spin orbit coupling, the motion of the hole along a certain direction is equivalent to the application of an effective magnetic field which induces in turn a coherent rotation of the heavy hole spin. The hole motion and consequently the quantum logic operation is initialized only by weak static voltages applied to the electrodes which cover the nanodevice. The proposed gates allow for an all electric and ultrafast (tens of picoseconds) heavy hole spin manipulation and give the possibility to implement a scalable architecture of heavy hole spin qubits for quantum computation applications.

cond-mat.mes-hall↗

arXiv2012

Spin Orbit Mediated Manipulation of Heavy Hole Spin Qubit in Gated Semiconductor Nanodevices

A novel spintronic nanodevice is proposed that is capable to manipulate the single heavy hole spin state in a coherent manner. It can act as a single quantum logic gate. The heavy hole spin transformations are realized by transporting the hole around closed loops defined by metal gates deposited on top of the nanodevice. The device exploits Dresselhaus spin orbit interaction which translates the spatial motion of the hole into a rotation of the spin. The proposed quantum gate operates on sub nanosecond time scales and requires only the application of a weak static voltage which allows for addressing heavy hole spin qubit individually. Our results are supported by quantum mechanical time dependent calculations within the four band Luttinger Kohn model.

cond-mat.mes-hall↗