Science Daily January 5, 2021 An international team of researchers (USA – Stanford University, Canada, Czech Republic, Spain, Germany) presents a temporal-mode demultiplexing scheme that achieves the ultimate quantum precision for the simultaneous estimation of the temporal centroid, the time offset, and the relative intensities of an incoherent mixture of ultrashort pulses at the single-photon level. They experimentally resolved temporal separations 10 times smaller than the pulse duration, as well as imbalanced intensities. This represents an improvement of more than an order of magnitude over the best standard methods based on intensity detection. The findings could allow significant improvements in […]
Tag Archives: Quantum technology
New quantum nanodevice can simultaneously act as a heat engine and a refrigerator
Phys.org December 28, 2020 An international team of researchers (Japan, Ukraine, USA – University of Michigan) has experimentally demonstrated the quantum version of the heat engine which uses an electron in a transistor. The electron has two possible energy states. The team could increase or decrease the gap between these energy states by applying an electric field and microwaves. This can be analogous to the periodic expanding–compressing operation of a fluid in a chamber. The device also emitted microwaves when the electron went from the high-energy level to the lower one. By monitoring whether the upper energy level was occupied, […]
Quantum insulators create multilane highways for electrons
Nanowerk December 16, 2020 In quantum anomalous Hall (QAH) insulators, electron flow is constrained to the edges, and electrons on one edge can only go in one direction and those on the other edge can only go the opposite direction. In prior studies, the QAH effect had been experimentally realized only in materials where the Chern number had a value of 1, essentially with a single two-lane highway for electrons. They observed some dissipation of current at connection points between QAH insulators and metallic electrodes, which occurs in the form of heat. However, by increasing the thickness of the QAH […]
Researchers create entangled photons 100 times more efficiently than previously possible
Phys.org December 17, 2020 Current methods of creating entanglement are inefficient, requiring a torrent of incoming laser light comprising hundreds of millions of photons before a single entangled photon pair will grudgingly drip out at the other end. Based on their earlier research, researchers at the Stevens Institute of Technology carved extremely high-quality racetrack-shaped microcavities into flakes of lithium niobate crystal. The cavities internally reflect photons with very little loss of energy, enabling light to circulate longer and interact with greater efficiency. By fine-tuning additional factors such as temperature, the team was able to create an unprecedentedly bright source of […]
Error-prone quantum bits could correct themselves, physicists show
Phys.org December 9, 2020 One of the chief obstacles facing quantum computer designers is correcting the errors that creep into a processor’s calculations. A team of researchers in the US (NIST, University of Maryland, Caltech) is experimenting with a photonic cavity resonator into which multiple photons can be driven to bounce back and forth between the cavity’s reflective walls. The photons combine to form ripple-like interference patterns. The patterns themselves contain the qubit’s information. Rather than construct an elaborate system to detect, measure and compensate for noise and errors, the team members perceived that if the supply of photons in […]
Researchers achieve quantum advantage
Phys.org December 9, 2020 An on-demand and truly scalable source of indistinguishable single photons is the essential component enabling high-fidelity photonic quantum operations. A main challenge is to overcome noise and decoherence processes to reach the steep benchmarks on generation efficiency and photon indistinguishability required for scaling up the source. An international team of researchers (Denmark, Germany) has developed a single-photon source featuring near-unity indistinguishability using a quantum dot in an “on-chip” planar nanophotonic waveguide circuit. The device produces long strings of >100 single photons without any observable decrease in the mutual indistinguishability between photons. They were able to generate […]
Scientists produce a quantum state that is part light and part matter
Nanowerk December 7, 2020 An international team of researchers (USA – University of Minnesota, University of Maryland, University of Colorado, Vanderbilt University, Spain) developed a unique process in which they achieved “ultra-strong coupling” between infrared light (photons) and matter (atomic vibrations) by trapping light in tiny, annular holes in a thin layer of gold. These nanocavities, like a highly scaled-down version of the coaxial cables that are used to send electrical signals. With this new process to engineer nanometer-sized version of coaxial cables, they are pushing the frontiers of ultra-strong coupling, which means they are discovering new quantum states where […]
Mapping quantum structures with light to unlock their capabilities
Nanowerk December 4, 2020 All-optical band-structure reconstruction could directly connect electronic structure with the coveted quantum phenomena if strong light waves transported localized electrons within preselected bands. An international team of researchers (USA – University of Michigan, Germany) has shown that harmonic sideband (HSB) generation in monolayer tungsten diselenide creates distinct electronic interference combs in momentum space. Locating these momentum combs in spectroscopy enables super-resolution tomography of key band-structure details in situ. They experimentally tuned the optical-driver frequency by a full octave and showed that the predicted super-resolution manifests in a critical intensity and frequency dependence of HSBs. The concept […]
Improving quantum dot interactions, one layer at a time
Science Daily November 20, 2020 Controlling interaction between quantum dots could greatly improve charge transport, leading to more efficient solar cells. Researchers fabricated CdTe quantum dot superlattices via the layer-by-layer assembly of positively charged polyelectrolytes and negatively charged CdTe quantum dots to control the dimension of the quantum resonance by independently changing the distances between quantum dots in the stacking (out-of-plane) and in-plane directions. They experimentally verified the miniband formation. The fabrication method can be used with other types of water-soluble quantum dots and nanoparticles. Combining different types of semiconductor quantum dots, or combining semiconductor quantum dots with other nanoparticles, […]
This Weird, Cheap Quantum Device Can Run For a Year With a Single Kick of Energy
Science Alert November 22, 2020 Continuous, battery-free operation of sensor nodes requires ultra-low-power sensing and data-logging techniques. According to the researchers at Washington University by directly coupling a sensor/transducer signal into globally asymptotically stable monotonic dynamical systems based on Fowler-Nordheim quantum tunneling, it is possible to achieve self-powered sensing at an energy budget that is currently unachievable using conventional energy harvesting methods. They have developed a device that uses a differential architecture to compensate for environmental variations and the device can retain sensed information for durations ranging from hours to days. With a theoretical operating energy budget less than 10 […]