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By using bright pulses of light to ‘blind’ the avalanche photodiode detectors used in quantum cryptography equipment, scientists in Europe have shown that it is possible to tracelessly steal the secret encryption key generated by such systems and thus compromise their security.
Coherent Rabi flopping and coherent pulse reshaping are directly observed in an operating quantum cascade laser. The findings indicate the potential for coherent effects to be exploited in mode locking, and may stimulate new approaches for generating short pulses in quantum cascade lasers.
Researchers describe a theoretical mechanism that may ensure high-fidelity entanglement of photons, and thus could be used to construct a practical quantum repeater. The communication rate is shown to be a function of the maximum distance between any two adjacent quantum repeaters, rather than of the entire length of the network.
Researchers demonstrate random-number generation by exploiting the intrinsic randomness of vacuum states. The approach may lead to reliable and high-speed quantum random-number generators for applications ranging from gambling to cryptography.
The ability of pulsed near-infrared laser light to pace the heart beat of a quail embryo is demonstrated, suggesting that such optical pacing may become a useful tool for developmental cardiology.
The effects of interactions on Hanbury Brown and Twiss interferometry are studied by considering the propagation of light in a nonlinear optical medium. The interactions affect the multipath interference, which makes it difficult to extract information about the light source. Nevertheless, the recovery of the disordered information is demonstrated through proper analysis.
Scientists improve the precision of time-of-flight measurements from several hundreds of micrometres to the nanometre regime by timing femtosecond pulses through phase-locking control of the pulse repetition rate using the optical cross-correlation technique. This result looks set to benefit synthetic aperture imaging for future space missions of formation-flying satellites and remote experiments involving the general theory of relativity.
Advanced on-chip photonic networks require integrated nanoscale lasers with low power consumption. Researchers have now demonstrated high-speed modulation of a compact heterostructure photonic crystal laser at room temperature with an unprecedented low required energy of ∼13 fJ per bit transmitted.
The Linac Coherent Light Source free-electron laser has now achieved coherent X-ray generation down to a wavelength of 1.2 Å and at a brightness that is nearly ten orders of magnitude higher than conventional synchrotrons. Researchers detail the first operation and beam characteristics of the system, which give hope for imaging at atomic spatial and temporal scales.
The effect of loss on quantum states is one of the major hurdles in quantum communications. A quantum error-correcting code that overcomes erasure due to photon loss is experimentally demonstrated. The scheme uses linear optics and protects a four-mode entangled mesoscopic state of light.
Optical spectral broadening prevents access to intrinsic physical phenomenon. A new experimental technique is demonstrated for measuring spectral diffusion based on photon correlations within a spectral line. The time resolution of the photoluminescence was 90 ps, which exceeds the current best reported resolution by four orders of magnitude.
Truly remote, independent InGaAs quantum dots are tuned to the same energy using large applied electric fields of up to −500 kV cm−1. This allows for two-photon interference of their emission under coincidence gating, and opens up the possibility of transferring quantum information between remote solid-state sources.
An ‘all-optical’ technique is proposed that can be used to detect broadband terahertz waves by coherently manipulating fluorescence emission from a gas plasma. This technique can be used to measure terahertz pulses at a distance of 10 m with unlimited directionality, even in the presence of water vapour absorption.
Non-Gaussian continuous variable operations are demonstrated for the first time at telecommunications wavelengths. Squeezed states were generated using a titanium superconducting sensor that can resolve the incident photon number. Reconstructed Wigner functions of the generated quantum states indicated non-Gaussian operation.
A terahertz quantum cascade laser and diode mixer are monolithically integrated to form a simple microelectronic terahertz transceiver. The performance of this system — the transmission of a coherent carrier, heterodyne reception of an external signal, frequency locking and tuning — is as efficient as that of discrete component terahertz photonic systems.
Researchers present the first heralded generation of photon states that are maximally entangled in polarization with linear optics. Three photon pairs are generated by spontaneous parametric down-conversion from β-barium borate crystals. The coincident detection of four auxiliary photons unambiguously heralds the successful preparation of the entangled state.
The phase locking of a longitudinal mode of a 2.7 THz quantum cascade laser was achieved using the spectral bandwidth of a mode-locked erbium-doped fibre laser. This technique is applicable to any terahertz quantum cascade laser source, and is an ideal tool for controlling the phase of different quantum cascade lasers.
Quasi-phase-matching (QPM) has always been thought of as a purely spatial phenomenon. Now, scientists show that QPM can be extended to the temporal domain, introducing temporal and spatiotemporal modulations of the nonlinear susceptibility. This concept paves the way for the manipulation of light through nonlinear interactions, and may have unique applications in nonlinear optics.
Researchers demonstrate coherent control of an exciton qubit in a semiconductor quantum dot through optoelectronic means. Such state manipulation of single quantum systems is essential for the development of quantum information systems.
Long-range surface plasmon propagation with net positive gain over macroscopic distances is directly observed. The gain is provided by an optically pumped layer of fluorescent conjugated polymer that is adjacent to the metal waveguide surface.
