Gao, J., McMillan, J. F., & Wong, C. W. (2012). Nanophotonics: Remote on-chip coupling. Nat. Photon., 6(1), 7–8.
Abstract: Scientists have demonstrated strongly coupled photon states between two distant high-Q photonic crystal cavities connected by a photonic crystal waveguide. Remote dynamic control over the coupled states could aid the development of delay lines, optical buffers and qubit operations in both classical and quantum information processing.
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Gabay, M., & Triscone, J. - M. (2011). Superconductors: Terahertz superconducting switch. Nat. Photon., 5(8), 447–449.
Abstract: The use of terahertz pulses to 'gate' interlayer charge transport in a superconductor could lead to a variety of new and interesting applications.
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Fuchs, G. D., Burkard, G., Klimov, P. V., & Awschalom, D. D. (2011). A quantum memory intrinsic to single nitrogen–vacancy centres in diamond. Nat. Phys., 7(10), 789–793.
Abstract: A quantum memory, composed of a long-lived qubit coupled to each processing qubit, is important to building a scalable platform for quantum information science. These two qubits should be connected by a fast and high-fidelity operation to store and retrieve coherent quantum states. Here, we demonstrate a room-temperature quantum memory based on the spin of the nitrogen nucleus intrinsic to each nitrogen–vacancy (NV) centre in diamond. We perform coherent storage of a single NV centre electronic spin in a single nitrogen nuclear spin using Landau–Zener transitions across a hyperfine-mediated avoided level crossing. By working outside the asymptotic regime, we demonstrate coherent state transfer in as little as 120 ns with total storage fidelity of 88±6%. This work demonstrates the use of a quantum memory that is compatible with scaling as the nitrogen nucleus is deterministically present in each NV centre defect.
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Freer, E. M., Grachev, O., Duan, X., Martin, S., & Stumbo, D. P. (2010). High-yield self-limiting single-nanowire assembly with dielectrophoresis. Nat. Nanotech., 5(7), 525–530.
Abstract: Single-crystal nanowire transistors and other nanowire-based devices could have applications in large-area and flexible electronics if conventional top-down fabrication techniques can be integrated with high-precision bottom-up nanowire assembly. Here, we extend dielectrophoretic nanowire assembly to achieve a 98.5% yield of single nanowires assembled over 16,000 patterned electrode sites with submicrometre alignment precision. The balancing of surface, hydrodynamic and dielectrophoretic forces makes the self-assembly process controllable, and a hydrodynamic force component makes it self-limiting. Our approach represents a methodology to quantify nanowire assembly, and makes single nanowire assembly possible over an area limited only by the ability to reproduce process conditions uniformly.
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Feofanov, A. K., Oboznov, V. A., Bol'Ginov, V. V., Lisenfeld, J., Poletto, S., Ryazanov, V. V., et al. (2010). Implementation of superconductor/ferromagnet/ superconductor. Nat. Phys., 6(8), 593–597.
Abstract: High operation speed and low energy consumption may allow the superconducting digital single-flux-quantum circuits to outperform traditional complementary metal-oxide-semiconductor logic. The remaining major obstacle towards high element densities on-chip is a relatively large cell size necessary to hold a magnetic flux quantum Φ0. Inserting a π-type Josephson junction in the cell is equivalent to applying flux Φ0/2 and thus makes it possible to solve this problem. Moreover, using π-junctions in superconducting qubits may help to protect them from noise. Here we demonstrate the operation of three superconducting circuits-two of them are classical and one quantum-that all utilize such π-phase shifters realized using superconductor/ferromagnet/superconductor sandwich technology. The classical circuits are based on single-flux-quantum cells, which are shown to be scalable and compatible with conventional niobium-based superconducting electronics. The quantum circuit is a π-biased phase qubit, for which we observe coherent Rabi oscillations. We find no degradation of the measured coherence time compared to that of a reference qubit without a π-junction.
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Fazal, F. M., & Block, S. M. (2011). Optical tweezers study life under tension. Nat. Photon., 5(6), 318–321.
Abstract: Optical tweezers have become one of the primary weapons in the arsenal of biophysicists, and have revolutionized the new field of single-molecule biophysics. Today's techniques allow high-resolution experiments on biological macromolecules that were mere pipe dreams only a decade ago.
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Dada, A. C., Leach, J., Buller, G. S., Padgett, M. J., & Andersson, E. (2011). Experimental high-dimensional two-photon entanglement and violations of generalized Bell inequalities. Nat. Phys., 7(9), 677–680.
Abstract: Quantum entanglement plays a vital role in many quantum-information and communication tasks. Entangled states of higher-dimensional systems are of great interest owing to the extended possibilities they provide. For example, they enable the realization of new types of quantum information scheme that can offer higher-information-density coding and greater resilience to errors than can be achieved with entangled two-dimensional systems (see ref. and references therein). Closing the detection loophole in Bell test experiments is also more experimentally feasible when higher-dimensional entangled systems are used. We have measured previously untested correlations between two photons to experimentally demonstrate high-dimensional entangled states. We obtain violations of Bell-type inequalities generalized to d-dimensional systems up to d=12. Furthermore, the violations are strong enough to indicate genuine 11-dimensional entanglement. Our experiments use photons entangled in orbital angular momentum, generated through spontaneous parametric down-conversion, and manipulated using computer-controlled holograms.
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Crespi, A., Ramponi, R., Osellame, R., Sansoni, L., Bongioanni, I., Sciarrino, F., et al. (2011). Integrated photonic quantum gates for polarization qubits. Nat. Comm., 2(566), 6.
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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Collins, M. J., Xiong, C., Rey, I. H., Vo, T. D., He, J., Shahnia, S., et al. (2013). Integrated spatial multiplexing of heralded single-photon sources. Nature Communications, .
Abstract: The non-deterministic nature of photon sources is a key limitation for single-photon quantum processors. Spatial multiplexing overcomes this by enhancing the heralded single-photon yield without enhancing the output noise. Here the intrinsic statistical limit of an individual source is surpassed by spatially multiplexing two monolithic silicon-based correlated photon pair sources in the telecommunications band, demonstrating a 62.4% increase in the her- alded single-photon output without an increase in unwanted multipair generation. We further demonstrate the scalability of this scheme by multiplexing photons generated in two waveguides pumped via an integrated coupler with a 63.1% increase in the heralded photon rate. This demonstration paves the way for a scalable architecture for multiplexing many photon sources in a compact integrated platform and achieving efficient two-photon inter- ference, required at the core of optical quantum computing and quantum communication protocols.
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Clerk, A. (2012). Quantum phononics: To see a SAW. Nat. Phys., 8(4), 256–257.
Abstract: Mechanical oscillations of microscopic resonators have recently been observed in the quantum regime. This idea could soon be extended from localized vibrations to travelling waves thanks to a sensitive probe of so-called surface acoustic waves.
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