Due to the rapid development of nano-science and technology as well as the new emerging research field of quantum information science, the designs of various nanoscale electronic and spintronic devices in recent years have been focused not only on how the device can rapidly turn on or off the electronic charge and spin currents, but  also  how  the  device  can  reliably  and  efficiently  manipulate  the  quantum coherence of electron charges and spins through external bias and gate voltage controls. Thus, the investigation of quantum non-equilibrium electronic transport dynamics has turned to be a main research topic in nano sciences. The relevant nano systems include various nanostructures, molecular electronic devices, spintronic devices, cold atoms devices, and nano-photonic and nano-bio systems. In this presentation, I will report some of recent progress we made. We developed a general theory of non-equilibrium theory for various nano devices [1-5]. The non-equilibrium dynamics is described by the exact master equation we developed, in which the back-reaction effects from environments are fully taking into account. We utilize this non-equolibrium theory to study quantum coherence and quantum transport control of single  electron  transistors  [6],  dot-quantum-dot  Aharonov-Bohm  interferometers [7-8,10-12] nano-photonic devices in photonic crystals [9], etc. Our exact master equation also allows to explore transient electronic charge and spin transport phenomena, from which we can provide the detailed temporal information on the mechanism of intrinsic and/or extrinsic loss of electron (charge and spin) and photon quantum coherence in nanostructures through transient transport.

References:
[1] Matisse W. Y. Tu and W. M. Zhang*, “Non-Markovian decoherence theory for a double quantum dot charge qubit”, Phys. Rev. B 78, 235311 (2008).
[2] Matisse Y. W. Tu, M. T. Lee and Wei-Min Zhang*, “Exact master equation and non-Markovian decoherence for quantum dot quantum computing” Invited article for the special issue “Quantum Decoherence and Entanglement”, Quantum Inf. Process (Springer), 8, 631-646 (2009).
[3] J. S. Jin, M. W. Y. Tu, W. M. Zhang*, and Y. J. Yan, “Non-equilibrium quantum theory for nanodevices”, New. J. Phys. 12, 083013 (2010).
[4] C. U Lei and W. M. Zhang*, “Quantum photonic dissipative transport theory”, Ann. Phys. 327, 1408 (2012).
[5] W. M. Zhang*, P. Y. Lo, H. N. Xiong, M. W. Y. Tu and F. Nori, “General non-Markovian Dynamics of open quantum systems”, Phys. Rev. Lett. 109, 170402 (2012).
[6] C. Y. Lin and Wei-Min Zhang*, "Single-electron turnstile pumping with high frequencies", Appl. Phys. Lett. 99, 072105 (2011).
[7] Matisse W.Y. Tu, Wei-Min Zhang* and F. Nori, “Coherent control of double-dot molecules using Aharonov-Bohm magnetic flux”, Phys. Rev. B 86, 195403 (2012).
[8] Matisse W.Y. Tu, Wei-Min Zhang*, J. S. Jin, O. Entin-Wohlman and A. Aharony, “Transient quantum transport in double-dot Aharonov-Bohm interferometers”, Phys. Rev. B 86, 115453 (2012).
[9] Xue, R. B. Wu, Wei-Min Zhang, J. Zhang and Tzyh-Jong Tarn, “Decoherence suppression via non-Markovian coherent feedback controls”, Phys. Rev. A 86, 052304 (2012).
[10] J. S. Jin, M. W. Y. Tu, N. E. Wang, and Wei-Min Zhang*, “Precision control of charge coherence in parallel double dot systems through spin-orbit interaction”, J. Chem. Phys. 139, 064706 (2013).
[11] P. Y. Yang, C. Y. Lin and Wei-Min Zhang*, “Transient current-current correlations and noise spectra”, Phys. Rev. B 89, 115411 (2014).
[12] Matisse W. Y. Tu, A. Aharony, Wei-Min Zhang*, and O. Entin-Wohlman, “Real-time dynamics of spin-dependent transport through a double-quantum-dot Aharonov-Bohm interferometer with spin-orbit interaction”, arXiv: 1406.6258 (2014).