Phys.org February 10, 2023 Satellite-based quantum links have been proposed to extend the network domain for quantum communication. An international team of researchers (USA – Oak Ridge National Laboratory, University of Illinois, Singapore) developed a quantum communication system, suitable for realistic satellite-to-ground communication and executed an entanglement-based quantum key distribution (QKD) protocol achieving quantum bit-error rates (QBERs) below 2% in all bases. They demonstrated low-QBER execution of a higher-dimensional hyperentanglement-based QKD protocol, using photons simultaneously entangled in polarization and time bin, leading to significantly higher secure key rates, at the cost of increased technical complexity and system size. They showed […]
Tag Archives: Quantum communications
Transporting of two-photon quantum states of light through a phase-separated Anderson localization optical fiber
Phys.org November 23, 2022 Experiments in the past have demonstrated Anderson localization in optical fibers, classical or conventional light, in two dimensions while propagating it through the third dimension. An international team of researchers (Spain, USA – industry, Italy) engineered the optical setup to send the quantum light through the phase-separated Anderson localization fiber and detected its arrival with the single-photon avalanche diode (SPAD) array camera. It enabled them not only to detect and identify them as pairs, as they arrived at the same time. As the pairs are quantum correlated, knowing where one of the two photons is detected […]
Microlaser chip adds new dimensions to quantum communication
Phys.org November 21, 2022 In quantum communications with qubits, the superposition makes it so a quantum pulse cannot be copied. However, with only two levels of superposition, qubits have limited storage space and low tolerance for interference. An international team of researchers (USA – University of Pennsylvania, Duke University, City University of New York, Spain, Italy) has created a chip that outstrips the security and robustness of existing quantum communications hardware. The device’s four-level qudits enable significant advances in quantum cryptography, raising the maximum secrete key rate for information exchange from 1 bit per pulse to 2 bits per pulse. […]
More efficient optical quantum gates
Phys.org May 13, 2022 Progress in optical quantum information processing is hampered by the low efficiency of the two-qubit quantum gates realized so far. Researchers in Germany demonstrated an optical two-qubit gate with an average efficiency above 40%, thus outperforming the previous record by a factor of almost 4. They accomplished this with electromagnetically induced transparency. Incoming photons are converted into polaritons in highly excited Rydberg state. Any two atoms in such a state have a strong interaction, even at large separations. When two photons enter the resonator, both become polaritons and their Rydberg components interact. When the excitations leave […]
Researchers Set Record by Preserving Quantum States in Silicon Carbide for More Than Five Seconds
SciTech Daily March 13, 2022 Inability to easily read the information held in qubits, and the short coherence of qubits are impediments to the many technological applications of quantum science such as hacker proof communications networks and quantum computers. An international team of researchers (USA – University of Chicago, Argonne National Laboratory, Japan, Sweden) has demonstrated single-shot readout of single defects in SiC via spin-to-charge conversion, whereby the defect’s spin state was mapped onto a long-lived charge state. With this technique, they achieved over 80% readout fidelity without pre- or post-selection, resulting in a high signal-to-noise ratio that enabled them […]
Two-dimensional material could store quantum information at room temperature
Phys.org February 11, 2022 Spins in two-dimensional materials offer an advantage, as the reduced dimensionality enables feasible on-chip integration into devices. An international team of researchers (UK, Australia) has reported room-temperature optically detected magnetic resonance (ODMR) from single carbon-related defects in hexagonal boron nitride with up to 100 times stronger contrast than the ensemble average. They identified two distinct bunching timescales in the second-order intensity-correlation measurements for ODMR-active defects, but only one for those without an ODMR response. They observed either positive or negative ODMR signal for each defect. Based on kinematic models, they related this bipolarity to highly tunable […]
New quantum transmission protocol has higher data transmission rate, robustness against interference
Phys.org September 22, 2021 One of the fundamental principles enabling entanglement-based quantum communication security is the fact that interfering with one photon will destroy entanglement and thus be detectable. However, this property is also the greatest obstacle. Random encounters of traveling photons, losses, and technical imperfections make noise an inevitable part of any quantum communication scheme, severely limiting distance, key rate, and environmental conditions in which quantum key distribution can be employed. Using photons entangled in their spatial degree of freedom, an international team of researchers (China, Austria, Canada, Czech Republic, Slovakia) has shown that the increased noise resistance of […]
Counting single photons at unprecedented rates
Phys.org April 13, 2021 Researchers at NIST have demonstrated a method that allows a high-efficiency single-photon-avalanche diode (SPAD) with a thick absorption region to count single photons at rates significantly higher than previously demonstrated. They applied large (>30 V) AC bias gates to the SPAD at 1 GHz and detected minute avalanches by means of radio frequency interferometry. They measured a reduction by a factor of ≈500 in the average charge per avalanche when compared to operation in its traditional active-quenching module and a relative increase in >19% in detection efficiency at 850 nm. The reduction in charge strongly suppresses self-heating effects in the […]
Researchers establish the first entanglement-based quantum network
Phys.org April 15, 2021 Researchers in the Netherlands have built a three-node entanglement-based quantum network by combining remote quantum nodes based on diamond communication qubits into a scalable phase-stabilized architecture, supplemented with a robust memory qubit and local quantum logic. They achieved real-time communication and feed-forward gate operations across the network. They demonstrated two quantum network protocols without postselection: the distribution of genuine multipartite entangled states across the three nodes, and entanglement swapping through an intermediary node. The work establishes a key platform for exploring, testing, and developing multinode quantum network protocols and a quantum network control stack…read more. TECHNICAL […]
A quantum internet is closer to reality, thanks to this switch
Phys.org March 2, 2021 In the emerging field of quantum networking, the need for effective resource provisioning is particularly acute, given the generally lower power levels, higher sensitivity to loss, and inapplicability of optical detection and retransmission. A team of researchers in the US (Purdue University, Oak Ridge National Laboratory) has demonstrated reconfigurable distribution of quantum entanglement in a four-user tabletop network. By adaptively partitioning bandwidth with a single wavelength-selective switch, they successfully equalized two-party coincidence rates that initially differed by over two orders of magnitude. Their scalable approach introduces loss that is fixed with the number of users, offering […]