TMR Network School on "Quantum Computation and Quantum Information Theory",
Villa Gualino, Torino, Italy, July 12 - 23, 1999.

NATO ASI School on "Quantum Mesoscopic Phenomena and Mesoscopic Devices in Microelectronics",
Ankara / Antalya, Turkey, June 13 - 25, 1999.

NATO ASI School "Topological Aspects of Low Dimensional Systems", Les Houches, July 7 - 31, 1998.

Visiting position at the Institute for Theoretical Physics, theoretical physics group of Prof. Anton Alexeev,
Uppsala University, Sweden, September 25 - October 25, 1998.

Visiting position at the Hokkaido University, theoretical physics group of Prof. Kenzo Ishikawa,
Sapporo, Japan, April - June 1996.

Quantum computing and quantum communication with electrons in nanostructures.

Transport and noise in multiterminal mesoscopic conductors.

Various talks presented during theoretical seminars at the Institute of Solid State Physics and the Institute of Microelectronics Technology, Chernogolovka, Russia.

Quantum computing and quantum communication with electrons in nanostructures.

Transport and noise in multiterminal mesoscopic conductors.

Quantum computing and quantum communication with electrons in nanostructures.

Classical and quantum noise in mesoscopic conductors.

Zero-bias diffusive anomalies in the presence of an external magnetic field.

Electrostatics of two-dimensional electron gases.

1. Transport and correlations in interacting nanoscale and mesoscopic systems. Phase coherence and theory of measurement; Spin transport and spin electronics; Shot noise; Coulomb blockade effect and cotunneling; Mesoscopic superconductivity; Luttinger liquid effects in 1D systems.

2. Physical realization of quantum computers. The goal is to find and bring to mesoscopic physics new ideas and concepts based on quantum computation and quantum information theory (e.g. non-locality, entanglement).

1. Noise of a Quantum-Dot System in the Cotunneling Regime [1]. We find that in contrast to sequential tunneling where the noise is either Poissonian or sub-Poissonian (suppressed by charge conservation on the quantum dot), the noise in inelastic cotunneling can be super-Poissonian. In the case of weak cotunneling we prove a non-equilibrium fluctuation-dissipation theorem which leads to a universal expression for the noise-to-current ratio. In order to investigate strong cotunneling we develop a microscopic theory of cotunneling based on the density-operator formalism and using the projection operator technique.

2. Resonant Transport of Non-Local Spin-Entangled Electrons [2]. We propose and analyze a spin entangling setup based on an superconductor coupled to two spatially separated quantum dots each of which is tunnel-coupled to outgoing normal leads. In the presence of an applied voltage bias and in the Coulomb

blockade regime two correlated electrons coherently tunnel from the superconductor via different dots into different leads due to the Andreev process. The spin-singlet coming from the Cooper pair remains preserved in this process, and the setup provides a source of mobile and nonlocal spin-entangled electrons. The transport is shown to be governed by a two-particle Breit-Wigner resonance which allows the injection of the two electrons at exactly the same energy which is a crucial requirement for a subsequent noise measurement [8].

3. Shot Noise by Quantum Scattering in Chaotic Cavities [4]. The work is done in collaboration with the experimental group from the University of Basel.

4. Quantum Dot as Spin Filter and Spin Memory [5]. We consider a quantum dot in the Coulomb blockade regime weakly coupled to leads and show that in the presence of a magnetic field the dot acts as an efficient spin-filter. Conversely, if the leads are fully spin-polarized the up or down state of the spin on the dot results in a large sequential or small cotunneling current, and thus, the setup can be operated as a single-spin memory.

5. Probing the entanglement and non-locality of electrons via transport and noise [6,8]. We have theoretically demonstrated that entanglement of two electrons in mesoscopic systems can be detected in transport and noise measurements, which are sensitive to the symmetry of a two-particle wave function. In particular, in the Coulomb blockade and cotunneling regime the singlet and triplet states in a double-dot lead to phase-coherent current and noise contributions of opposite signs and to Aharonov-Bohm and Berry phase oscillations in response to magnetic fields. These oscillations are a genuine two-particle effect and provide a direct measure of non-locality in entangled states. In a beam splitter set-up [8] the shot noise is shown to be sensitive to the symmetry of a two-electron wave function, and thus it can be used to detect the entanglement. Fermi liquid effects in the transport of entangled electrons are studied, and z-factor of 2D electrons is calculated.

6. Shot noise in diffusive conductors and chaotic cavities [11,12,14,15]. One of the central results of this work is the universality of the shot noise in multiterminal diffusive conductors and chaotic cavities proven within the Boltzmann-Langevin equation approach and using the principle of minimal correlations. A new phenomena in which current noise is induced by spin transport [8,12] and thermal transport [14] are discussed.

[1] Noise of a Quantum-Dot System in the Cotunneling Regime,
Eugene V. Sukhorukov, Daniel Loss, and Guido Burkard, cond-mat/0010458.

[2] Andreev-Tunneling, Coulomb Blockade, and Resonant Transport of Non-Local Spin-Entangled Electrons,
Patrik Recher, Eugene V. Sukhorukov, and Daniel Loss, cond-mat/0009452.

[3] Spintronics and Spin-based Qubits in Quantum Dots,
Eugene V. Sukhorukov and Daniel Loss. To be published in Proceedings of the QD 2000, July 31 - August 3, 2000 Munich, Germany (special issue of Physica Status Solidi in March 2001).

[4] Shot Noise by Quantum Scattering in Chaotic Cavities,
S. Oberholzer, E.V. Sukhorukov, C. Strunk, C. Schonenberger, T. Heinzel, K. Ensslin, and M. Holland; cond-mat/0009087.

[5] Quantum Dot as Spin Filter and Spin Memory,
Patrik Recher, Eugene V. Sukhorukov, and Daniel Loss. Phys. Rev. Lett. 85 (2000) 1962-1965; cond-mat /0003089.

[6] Probing entanglement and non-locality of electrons in a double-dot via transport and noise,
D. Loss, and E.V. Sukhorukov. Phys. Rev. Lett. 84 (2000) 1035-1038; cond-mat/9907129.

[7] Quantum computation and spin electronics,
D.P. DiVincenzo, G. Burkard, D. Loss, and E.V. Sukhorukov. To be published in "Quantum Mesoscopic Phenomena and Mesoscopic Devices in Microelectronics", ed. I. O. Kulik (NATO Advanced Study Institute, Turkey, June 13-25, 1999).; cond-mat/9911245.

[8] Noise of entangled electrons: bunching and antibunching,
G. Burkard, D. Loss, and E.V. Sukhorukov. Phys. Rev. B 61 (2000) R16303-R16306; cond-mat/9906071.

[9] Transport and noise of entangled electrons,
E.V. Sukhorukov, D. Loss, G. Burkard. Proceedings of the XVI Sitges Conference (1999) "Statistical and dynamical aspects of mesoscopic systems", ed. D. Reguera et al., (Lecture Notes in Physics, Springer, 2000); cond-mat/9909348.

[10] Quantum computing and quantum communication with electrons in nanostructures,
D. Loss, G. Burkard, E.V. Sukhorukov. To be published in the proceedings of the XXXIVth Rencontres de Moriond (1999) "Quantum physics at mesoscopic scale"; cond-mat/9907133.

[11] Semi-classical theory of conductance and noise in open chaotic cavities,
Ya.M. Blanter, E.V. Sukhorukov. Phys. Rev. Lett. 84 (2000) 1280-1283; cond-mat/9904448.

[12] Transport and noise in multiterminal diffusive conductors,
E.V. Sukhorukov, and D. Loss. To appear in "Quantum Mesoscopic Phenomena and Mesoscopic Devices in Microelectronics", ed. I. O. Kulik (NATO Advanced Study Institute, Turkey, June 13-25, 1999).

[13] Magnetic-field-dependent zero-bias diffusive anomaly in Pb oxide-n-InAs structures: Coexistence of two- and three-dimensional states,
G.M. Minkov, A.V. Germanenko, S.A. Negachev, O.E. Rut, and E.V. Sukhorukov. Phys. Rev. B59 (1999) 13139-13146; cond-mat/9807041.

[14] Noise in multiterminal diffusive conductors: universality, nonlocality and exchange effects,
E.V. Sukhorukov, and D. Loss. Phys. Rev. B59 (1999) 13054-13066; cond-mat/9809239.

[15] Universality of shot noise in multiterminal diffusive conductors,
E.V. Sukhorukov, and D. Loss. Phys. Rev. Lett. 80 (1998) 4959-4962; cond-mat/9802050.

[16] Anisotropy of zero-bias diffusive anomalies for different orientations of the external magnetic field,
E.V. Sukhorukov, and A.V. Khaetskii. Phys. Rev. B56 (1997) 1456-1460; cond-mat/9704195.

[17] Edge magnetoplasmons in 2D electron systems with small filling factor,
V.B. Shikin, T. Vasilyeva, and E.V. Sukhorukov. Phys. Low-Dim. Struct. 7/8 (1996) 77-80.

[18] Modeling the patterned two-dimensional electron gas. Electrostatics.
J.H. Davies, I.A. Larkin, and E.V. Sukhorukov. J. Appl. Phys. 77 (1995) 4504-4512.

[19] STM conductance jumps at ambient conditions,
V.V. Dremov, S.Yu. Shapoval, E.V. Sukhorukov. Phys. Low-Dim. Struct. 11/12 (1994) 29-36.

[20] Method to investigate the random potential in a quantum point contact.
I.A. Larkin, E.V. Sukhorukov. Phys. Rev. B49 (1994) 5498-5507.

[21] Short-range impurity in a magnetic field: The conductance of a narrow channel.
E.V. Sukhorukov, C. Kunze, M.I. Lubin, Y. Levinson. Phys. Rev. B49 (1994) 17191-17198.

[22] Bound states near a short-range impurity in crossed magnetic and electric fields,
C. Kunze, Y.B. Levinson, M.I. Lubin, and E.V. Sukhorukov. Sov. Phys. JETP Lett. 56 (1992) 56-60.

[23] The effect of a short-range impurity on a saddle-point potential microjunction,
Y.B. Levinson, M.I. Lubin, and E.V. Sukhorukov. Fiz. Nizk. Temp. 18 (1992) 653-654.

[24] Short-range impurity in a saddle-point potential. The conductance of a microjunction,
Y.B. Levinson, M.I. Lubin, and E.V. Sukhorukov. Phys. Rev. B45 (1992) 11936-11943.

[25] Impurity-assisted tunneling in a quantum ballistic microconstriction,
Y.B. Levinson, M.I. Lubin, and E.V. Sukhorukov. Sov. Phys. JETP Lett. 54 (1991) 401-405.

[26] Bending of electron edge states in a magnetic field,
Y.B. Levinson, and E.V. Sukhorukov. J. Phys.: Condens. Matter 3 (1991) 7291-7306.

[27] Scattering of electron edge states in a magnetic field by small irregularities of the boundary,
Y.B. Levinson, and E.V. Sukhorukov. Phys. Lett. A149 (1990) 167-171.

[28] Nonlocal nature of the resistance in classical ballistic transport,
E.V. Sukhorukov, Y.B. Levinson. Sov. Phys. JETP 70 (1990) 782-786.

[29] Resistance of the ballistic microjunction in the metals with an anisotropic Fermi surface,
E.V. Sukhorukov, and A.V. Khaetskii. Fiz. Tverd. Tela 30 (1988) 1098-1101.

[30] Oscillations in the transverse magnetoresistance of a point contact,
Y.B. Levinson, E.V. Sukhorukov, A.V. Khaetskii. Sov. Phys. JETP Lett. 45 (1987) 488-490.