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| Author |
Lupascu, Adrian |
| Title |
Nonlinear dynamics: Quantum pendula locked in |
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Journal Article |
| Year |
2011 |
Publication |
Nature Physics |
Abbreviated Journal |
Nat. Phys. |
| Volume |
7 |
Issue |
2 |
Pages |
100-101 |
Keywords  |
fromIPMRAS |
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A study of the autoresonant behaviour of a superconducting pendulum reveals that quantum fluctuations determine only the initial oscillator motion and not its subsequent dynamics. This could be important in the development of more efficient methods for reading solid-state qubits. |
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840 |
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Nevou, L.; Liverini, V.; Friedli, P.; Castellano, F.; Bismuto, A.; Sigg, H.; Gramm, F.; Müller, E.; Faist, J. |
| Title |
Current quantization in an optically driven electron pump based on self-assembled quantum dots |
Type |
Journal Article |
| Year |
2011 |
Publication |
Nature Physics |
Abbreviated Journal |
Nat. Phys. |
| Volume |
7 |
Issue |
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Pages |
423–427 |
| Keywords |
fromIPMRAS |
| Abstract |
The electronic structure of self-assembled semiconductor quantum dots consists of discrete atom-like states that can be populated with a well-defined number of electrons. This property can be used to fabricate a d.c. current standard that enables the unit of ampere to be independently defined. Here we report an optically pumped current source based on self-assembled InAs/GaAs quantum dots. The accuracy obtained so far is 10–1 and is limited by the uncertainty in the number of dots. At 10 K the device generates a current difference of 2.39 nA at a frequency of 1 kHz. The accuracy could be improved by site-selective growth techniques where the number of dots is fixed by pre-patterning. The results are promising for applications in electrical metrology, where a current standard is needed to close the so-called quantum metrological triangle. |
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841 |
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Ma, Xiao-Song; Dakic, Borivoje; Naylor, William; Zeilinger, Anton; Walther, Philip |
| Title |
Quantum simulation of the wavefunction to probe frustrated Heisenberg spin systems |
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Journal Article |
| Year |
2011 |
Publication |
Nature Physics |
Abbreviated Journal |
Nat. Phys. |
| Volume |
7 |
Issue |
5 |
Pages |
399-405 |
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fromIPMRAS |
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Quantum simulators are controllable quantum systems that can reproduce the dynamics of the system of interest in situations that are not amenable to classical computers. Recent developments in quantum technology enable the precise control of individual quantum particles as required for studying complex quantum systems. In particular, quantum simulators capable of simulating frustrated Heisenberg spin systems provide platforms for understanding exotic matter such as high-temperature superconductors. Here we report the analogue quantum simulation of the ground-state wavefunction to probe arbitrary Heisenberg-type interactions among four spin-1/2 particles. Depending on the interaction strength, frustration within the system emerges such that the ground state evolves from a localized to a resonating-valence-bond state. This spin-1/2 tetramer is created using the polarization states of four photons. The single-particle addressability and tunable measurement-induced interactions provide us with insights into entanglement dynamics among individual particles. We directly extract ground-state energies and pairwise quantum correlations to observe the monogamy of entanglement. |
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842 |
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Zhang, Qiang; Goebel, Alexander; Wagenknecht, Claudia; Chen, Yu-Ao; Zhao, Bo; Yang, Tao; Mair, Alois; Schmiedmayer, Jörg; Pan, Jian-Wei |
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Experimental quantum teleportation of a two-qubit composite system |
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Journal Article |
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2006 |
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Nature Physics |
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Nat. Phys. |
| Volume |
2 |
Issue |
10 |
Pages |
678-682 |
| Keywords |
fromIPMRAS; quantum teleportation |
| Abstract |
Quantum teleportation, a way to transfer the state of a quantum system from one location to another, is central to quantum communication and plays an important role in a number of quantum computation protocols. Previous experimental demonstrations have been implemented with single photonic or ionic qubits. However, teleportation of single qubits is insufficient for a large-scale realization of quantum communication and computation. Here, we present the experimental realization of quantum teleportation of a two-qubit composite system. In the experiment, we develop and exploit a six-photon interferometer to teleport an arbitrary polarization state of two photons. The observed teleportation fidelities for different initial states are all well beyond the state estimation limit of 0.40 for a two-qubit system. Not only does our six-photon interferometer provide an important step towards teleportation of a complex system, it will also enable future experimental investigations on a number of fundamental quantum communication and computation protocols |
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RPLAB @ gujma @ |
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795 |
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Wei, Jian; Olaya, David; Karasik, Boris S.; Pereverzev, Sergey V.; Sergeev, Andrei V.; Gershenson, Michael E. |
| Title |
Ultrasensitive hot-electron nanobolometers for terahertz astrophysics |
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Journal Article |
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2008 |
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Nature Nanotechnology |
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Nature Nanotech |
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3 |
Issue |
8 |
Pages |
496-500 |
| Keywords |
HEB, Ti/NbN, single terahertz photons, detection |
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The submillimetre or terahertz region of the electromagnetic spectrum contains approximately half of the total luminosity of the Universe and 98% of all the photons emitted since the Big Bang. This radiation is strongly absorbed in the Earth's atmosphere, so space-based terahertz telescopes are crucial for exploring the evolution of the Universe. Thermal emission from the primary mirrors in these telescopes can be reduced below the level of the cosmic background by active cooling, which expands the range of faint objects that can be observed. However, it will also be necessary to develop bolometers – devices for measuring the energy of electromagnetic radiation—with sensitivities that are at least two orders of magnitude better than the present state of the art. To achieve this sensitivity without sacrificing operating speed, two conditions are required. First, the bolometer should be exceptionally well thermally isolated from the environment;
second, its heat capacity should be sufficiently small. Here we demonstrate that these goals can be achieved by building a superconducting hot-electron nanobolometer. Its design eliminates the energy exchange between hot electrons and the leads by blocking electron outdiffusion and photon emission. The thermal conductance between hot electrons and the thermal bath, controlled by electron–phonon interactions, becomes very small at low temperatures (10-16 WK-1 at 40 mK). These devices, with a heat capacity of 10-19 J K-1, are sufficiently sensitive to detect single terahertz photons in submillimetre astronomy and other applications based on quantum calorimetry and photon counting. |
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1748-3387 |
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576 |
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