Distributed Quantum Computation Architecture Using Semiconductor Nanophotonics

In a large-scale quantum computer, the cost of communications will dominate the performance and resource requirements, place many severe demands on the technology, and constrain the architecture. Unfortunately, fault-tolerant computers based entirely on photons with probabilistic gates, though equipped with "built-in" communication, have very large resource overheads; likewise, computers with reliable probabilistic gates between photons or quantum memories may lack sufficient communication resources in the presence of realistic optical losses. Here, we consider a compromise architecture, in which semiconductor spin qubits are coupled by bright laser pulses through nanophotonic waveguides and cavities using a combination of frequent probabilistic and sparse determinstic entanglement mechanisms. The large photonic resource requirements incurred by the use of probabilistic gates for quantum communication are mitigated in part by the potential high-speed operation of the semiconductor nanophotonic hardware. The system employs topological cluster-state quantum error correction for achieving fault-tolerance. Our results suggest that such an architecture/technology combination has the potential to scale to a system capable of attacking classically intractable computational problems.Comment: 29 pages, 7 figures; v2: heavily revised figures improve architecture presentation, additional detail on physical parameters, a few new reference

Electron and nuclear spin dynamics in fluorine-doped ZnSe epilayers

Electron spins in semiconductors are considered as candidates for quantum bits. This thesis presents a study of the spin dynamics of the strongly localized donor-bound electrons in fluorine-doped ZnSe epilayers via pump-probe Kerr rotation technique. A method exploiting the spin inertia is developed and used to measure the longitudinal spin relaxation time (T1). The excitation of the same samples with helicity-modulated laser pulses results in a transverse nuclear spin polarization, which was detected as a change of the Larmor precession frequency of the donor-bound electron spins in a magnetic field applied in the Voigt geometry. A mechanism of optically induced nuclear spin polarization is suggested based on the concept of resonant nuclear spin cooling driven by the inhomogeneous Knight field of the donor-bound electron. The all-optical induction and detection of the nuclear spin polarization allow us to measure the T1 time of the selenium-77 isotope. We combine the optical technique with radio frequency methods to measure the inhomogeneous spin dephasing time and the coherence time T2 of the selenium-77 isotope. While the T1 time is on the order of several milliseconds, the T2 time is several hundred microseconds. This verifies the validity of the classical model of nuclear spin cooling describing the optically induced nuclear spin polarization

NIR-emissive Alkynylplatinum(II) Terpyridyl Complex as a turn-on selective probe for heparin quantification by induced helical self-assembly behaviour

The extent of self-assembly viametal–metal and π-π stacking interactions, induced by the polyanionic biopolymers, enables the class of alkynylplatinum(II) terpyridyl complexes to be applicable for the sensing of important biomacromolecules through the monitoring of spectral changes. Strong demand arises for the design of selective and practical detection techniques for the quantification of heparin, a highly negative-charged polysaccharidethat can function as anticoagulant, due to the prevention of hemorrhagic complications upon overdose usage.Aconvenient sensing protocol for the detection of UFH and LMWH, two common forms of heparins in clinical use, in buffer and biological medium has been demonstrated with the spectral changes associated with the induced self-assembly of a NIR-emissive platinum(II) complex. The detection range has been demonstrated to cover clinical dosage levels and the structurally similar analogues can be effectively differentiated based on their anionic charge density and the formation of supramolecular helical assembly of the platinum(II) complex with them ...postprin

Induced self-assembly and Förster Resonance Energy Transfer Studies of Alkynylplatinum(II) Terpyridine Complex through interaction with water-soluble Poly(phenylene ethynylene sulfonate) and the proof-of-principle demonstration of this two-component ensemble for selective label-free detection of Human Serum Albumin (HSA)

The interaction of conjugated polyelectrolyte, PPE-SO3−, with platinum(II) complexes, [Pt(tpy)(C≡CC6H4CH2NMe3-4)](OTf)2 (1) and [Pt(tpy)(C≡C–CH2NMe3)](OTf)2 (2), has been studied by UV–vis, and steady-state and time-resolved emission spectroscopy. A unique FRET from PPE-SO3−to the aggregated complex 1on the polymer chain with PtfflfflfflPt interactionhas been demonstrated, resulting in the growth of triplet metal-metal-to-ligand charge transfer (3MMLCT) emission ...postprin

Amphiphilic Anionic Pt(II) Complexes: from spectroscopic to morphological changes

A new class of amphiphilic anionic platinum(II) bzimpy complexes has been demonstrated to show aggregation in water through PtfflfflfflPt and π–π stacking interactions. An interesting aggregation–partial deaggregation–aggregation process and a morphological transformation from vesicles to nanofibers have been demonstrated. These changes can be systematically controlled by the variation of solvent composition and could readily be probed by UV-vis absorption, emission, NMR, transmission electron microscopy and even with our naked eyes ...postprin