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| Author |
Schwarz, Brent |
| Title |
Lidar: Mapping the world in 3D |
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Journal Article |
| Year |
2010 |
Publication |
Nature Photonics |
Abbreviated Journal |
Nat. Photon. |
| Volume |
4 |
Issue |
7 |
Pages |
429-430 |
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LIDAR |
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A high-definition LIDAR system with a rotating sensor head containing 64 semiconductor lasers allows the efficient generation of 3D environment maps at unprecedented levels of detail. |
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RPLAB @ gujma @ |
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696 |
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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 |
| Year |
2008 |
Publication |
Nature Nanotechnology |
Abbreviated Journal |
Nature Nanotech |
| Volume |
3 |
Issue |
8 |
Pages |
496-500 |
| Keywords |
HEB, Ti/NbN, single terahertz photons, detection |
| Abstract |
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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Zhang, Qiang; Goebel, Alexander; Wagenknecht, Claudia; Chen, Yu-Ao; Zhao, Bo; Yang, Tao; Mair, Alois; Schmiedmayer, Jörg; Pan, Jian-Wei |
| Title |
Experimental quantum teleportation of a two-qubit composite system |
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Journal Article |
| Year |
2006 |
Publication |
Nature Physics |
Abbreviated Journal |
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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Peruzzo, Alberto; Laing, Anthony; Politi, Alberto; Rudolph, Terry; O'Brien, Jeremy L. |
| Title |
Multimode quantum interference of photons in multiport integrated devices |
Type |
Journal Article |
| Year |
2011 |
Publication |
Nature Communications |
Abbreviated Journal |
Nat. Comm. |
| Volume |
2 |
Issue |
224 |
Pages |
6 |
| Keywords |
fromIPMRAS |
| Abstract |
Photonics is a leading approach in realizing future quantum technologies and recently, optical waveguide circuits on silicon chips have demonstrated high levels of miniaturization and performance. Multimode interference (MMI) devices promise a straightforward implementation of compact and robust multiport circuits. Here, we show quantum interference in a 2×2 MMI coupler with visibility of V=95.6+/-0.9%. We further demonstrate the operation of a 4×4 port MMI device with photon pairs, which exhibits complex quantum interference behaviour. We have developed a new technique to fully characterize such multiport devices, which removes the need for phase-sensitive measurements and may find applications for a wide range of photonic devices. Our results show that MMI devices can operate in the quantum regime with high fidelity and promise substantial simplification and concatenation of photonic quantum circuits. |
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RPLAB @ gujma @ |
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763 |
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Ikuta, Rikizo; Kusaka, Yoshiaki; Kitano, suyoshi; Kato, Hiroshi; Yamamoto, Takashi; Koashi, Masato; Imoto, Nobuyuki |
| Title |
Wide-band quantum interface for visible-totelecommunication wavelength conversion |
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Journal Article |
| Year |
2011 |
Publication |
Nature Communications |
Abbreviated Journal |
Nat. Comm. |
| Volume |
2 |
Issue |
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Pages |
5 |
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fromIPMRAS |
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Although near-infrared photons in telecommunication bands are required for long-distance quantum communication, various quantum information tasks have been performed by using visible photons for the past two decades. Recently, such visible photons from diverse media including atomic quantum memories have also been studied. Optical frequency down-conversion from visible to telecommunication bands while keeping the quantum states is thus required for bridging such wavelength gaps. Here we report demonstration of a quantum interface of frequency down-conversion from visible to telecommunication bands by using a nonlinear crystal, which has a potential to work over wide bandwidths, leading to a high-speed interface of frequency conversion. We achieved the conversion of a picosecond visible photon at 780 nm to a 1,522-nm photon, and observed that the conversion process retained entanglement between the down-converted photon and another photon. |
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RPLAB @ gujma @ |
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764 |
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Crespi, Andrea; Ramponi, Roberta; Osellame, Roberto; Sansoni, Linda; Bongioanni, Irene; Sciarrino, Fabio; Vallone, Giuseppe; Mataloni, Paolo |
| Title |
Integrated photonic quantum gates for polarization qubits |
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Journal Article |
| Year |
2011 |
Publication |
Nature Communications |
Abbreviated Journal |
Nat. Comm. |
| Volume |
2 |
Issue |
566 |
Pages |
6 |
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fromIPMRAS |
| Abstract |
The ability to manipulate quantum states of light by integrated devices may open new perspectives both for fundamental tests of quantum mechanics and for novel technological applications. However, the technology for handling polarization-encoded qubits, the most commonly adopted approach, is still missing in quantum optical circuits. Here we demonstrate the first integrated photonic controlled-NOT (CNOT) gate for polarization-encoded qubits. This result has been enabled by the integration, based on femtosecond laser waveguide writing, of partially polarizing beam splitters on a glass chip. We characterize the logical truth table of the quantum gate demonstrating its high fidelity to the expected one. In addition, we show the ability of this gate to transform separable states into entangled ones and vice versa. Finally, the full accessibility of our device is exploited to carry out a complete characterization of the CNOT gate through a quantum process tomography. |
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RPLAB @ gujma @ |
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765 |
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Berlín, Guido; Brassard, Gilles; Bussières, Félix; Godbout, Nicolas; Slater, Joshua A.; Tittel, Wolfgang |
| Title |
Experimental loss-tolerant quantum coin flipping |
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Journal Article |
| Year |
2011 |
Publication |
Nature Communications |
Abbreviated Journal |
Nat. Comm. |
| Volume |
2 |
Issue |
561 |
Pages |
7 |
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fromIPMRAS |
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Coin flipping is a cryptographic primitive in which two distrustful parties wish to generate a random bit to choose between two alternatives. This task is impossible to realize when it relies solely on the asynchronous exchange of classical bits: one dishonest player has complete control over the final outcome. It is only when coin flipping is supplemented with quantum communication that this problem can be alleviated, although partial bias remains. Unfortunately, practical systems are subject to loss of quantum data, which allows a cheater to force a bias that is complete or arbitrarily close to complete in all previous protocols and implementations. Here we report on the first experimental demonstration of a quantum coin-flipping protocol for which loss cannot be exploited to cheat better. By eliminating the problem of loss, which is unavoidable in any realistic setting, quantum coin flipping takes a significant step towards real-world applications of quantum communication. |
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RPLAB @ gujma @ |
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766 |
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Knee, George C.; Simmons, Stephanie; Gauger, Erik M.; Morton, John J. L.; Riemann, Helge; Abrosimov, Nikolai V.; Becker, Peter; Pohl, Hans-Joachim; Itoh, Kohei M.; Thewalt, Mike L. W.; Briggs, G. Andrew D.; Benjamin, Simon C. |
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Violation of a Leggett–Garg inequality with ideal non-invasive measurements |
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Journal Article |
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2012 |
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Nature Communications |
Abbreviated Journal |
Nat. Comm. |
| Volume |
3 |
Issue |
606 |
Pages |
6 |
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fromIPMRAS |
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The quantum superposition principle states that an entity can exist in two different states simultaneously, counter to our 'classical' intuition. Is it possible to understand a given system's behaviour without such a concept? A test designed by Leggett and Garg can rule out this possibility. The test, originally intended for macroscopic objects, has been implemented in various systems. However to date no experiment has employed the 'ideal negative result' measurements that are required for the most robust test. Here we introduce a general protocol for these special measurements using an ancillary system, which acts as a local measuring device but which need not be perfectly prepared. We report an experimental realization using spin-bearing phosphorus impurities in silicon. The results demonstrate the necessity of a non-classical picture for this class of microscopic system. Our procedure can be applied to systems of any size, whether individually controlled or in a spatial ensemble. |
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RPLAB @ gujma @ |
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767 |
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Smith, Devin H.; Gillett, Geoff; de Almeida, Marcelo P.; Branciard, Cyril; Fedrizzi, Alessandro; Weinhold, Till J.; Lita, Adriana; Calkins, Brice; Gerrits, Thomas; Wiseman, Howard M.; Nam, Sae Woo; White, Andrew G. |
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Conclusive quantum steering with superconducting transition-edge sensors |
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Journal Article |
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2012 |
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Nature Communications |
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Nat. Comm. |
| Volume |
3 |
Issue |
625 |
Pages |
6 |
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fromIPMRAS |
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Quantum steering allows two parties to verify shared entanglement even if one measurement device is untrusted. A conclusive demonstration of steering through the violation of a steering inequality is of considerable fundamental interest and opens up applications in quantum communication. To date, all experimental tests with single-photon states have relied on post selection, allowing untrusted devices to cheat by hiding unfavourable events in losses. Here we close this 'detection loophole' by combining a highly efficient source of entangled photon pairs with superconducting transition-edge sensors. We achieve an unprecedented ~62% conditional detection efficiency of entangled photons and violate a steering inequality with the minimal number of measurement settings by 48 s.d.s. Our results provide a clear path to practical applications of steering and to a photonic loophole-free Bell test. |
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RPLAB @ gujma @ |
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768 |
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Ghali, Mohsen; Ohtani1, Keita; Ohno, Yuzo; Ohno, Hideo |
| Title |
Generation and control of polarization-entangled photons from GaAs island quantum dots by an electric field |
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Journal Article |
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2012 |
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Nature Communications |
Abbreviated Journal |
Nat. Comm. |
| Volume |
3 |
Issue |
661 |
Pages |
6 |
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fromIPMRAS |
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Semiconductor quantum dots are potential sources for generating polarization-entangled photons efficiently. The main prerequisite for such generation based on biexciton-exciton cascaded emission is to control the exciton fine-structure splitting. Among various techniques investigated for this purpose, an electric field is a promising means to facilitate the integration into optoelectronic devices. Here we demonstrate the generation of polarization-entangled photons from single GaAs quantum dots by an electric field. In contrast to previous studies, which were limited to In(Ga)As quantum dots, GaAs island quantum dots formed by a thickness fluctuation were used because they exhibit a larger oscillator strength and emit light with a shorter wavelength. A forward voltage was applied to a Schottky diode to control the fine-structure splitting. We observed a decrease and suppression in the fine-structure splitting of the studied single quantum dot with the field, which enabled us to generate polarization-entangled photons with a high fidelity of 0.72 ± 0.05. |
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