Phys.org March 25, 2024 An on-demand source of bright entangled photon pairs is needed for quantum key distribution (QKD) and quantum repeaters. The generation of such pairs is based on spontaneous parametric down-conversion (SPDC) in non-linear crystals. However, SPDC pair extraction efficiency is very limited when operating at near-unity fidelity. In principle quantum dots in photonic nanostructures can overcome this limit, but the devices with high entanglement fidelity have low pair extraction efficiency. An international team of researchers (Canada, the Netherlands, Sweden) has demonstrated a measured peak entanglement fidelity of 97.5% ± 0.8% and pair extraction efficiency of 0.65% from an InAsP […]
Tag Archives: Secure communication
Protecting light communication with random objects
Phys.org July 17, 2023 Researchers in the Netherlands have developed an optical communication system with two scattering layers to hide both the sender and receiver, by measuring the correlation of the intermediate speckle generated between the two layers. The binary message is modulated as spatially shaped wavefronts, and the high number of transmission modes of the scattering layers allowed for many uncorrelated incident wavefronts to send the same message, making it difficult for an attacker to intercept or decode the message and thus increasing secrecy. They collected 50,000 intermediate speckle patterns and analyzed their correlation distribution using the Kolmogorov-Smirnov (K-S) […]
Quantum leap for research into unhackable communications networks
Phys.org November 30, 2022 Quantum steering relaxes the strict technological constraints of Bell nonlocality by reframing it in an asymmetric manner, with a trusted party only on one side. However, tests of quantum steering still require either extremely high-quality entanglement or very low loss. An international team of researchers (UK, Switzerland) constructed a test of quantum steering for qudits harnessing the advantages of high-dimensional entanglement to be simultaneously noise robust and loss tolerant. It was designed for single-detector measurements and was able to close the fair-sampling loophole in a time-efficient manner. They demonstrated quantum steering in up to 53 dimensions, […]
Strange new phase of matter created in quantum computer acts like it has two time dimensions
Phys.org July 20, 2022 An international team of researchers (USA -research organization, UT Austin, UMass Amherst, Canada) has demonstrated an emergent dynamical symmetry-protected topological phase using an array of 10 trapped-ion of yitterbium as quantum processor. Each ion is individually held and controlled by electric fields produced by an ion trap and can be manipulated or measured using laser pulses. This phase showed edge qubits that are dynamically protected from control errors, crosstalk, and stray fields. The edge protection relies purely on emergent dynamical symmetries that are stable to generic coherent perturbations. The work paves the way for implementation of […]
Novel fluorescent organohydrogel proposed to achieve dual information encryption
Phys.org June 10, 2022 Researchers in China designed an organohydrogel by constructing interpenetrating organohydrogel networks, in which naphthylamide moieties (DEAN, green-yellow emission) are introduced in hydrophilic poly(N,N-dimethylacrylamide) (PDMA) hydrogel network and anthracene units (blue emission) are copolymerized in hydrophobic polystearate methacrylate (PSMA) organogel network. UV light of 365 nm triggers the unimer–dimer transition and leads the fluorescent color of organohydrogel to change from blue to faint yellow. Photomasks store the secret information. They achieved dual encryption by combining crystallization-induced shape memory performance. According to the researchers fluorescent organohydrogel provides a new idea for fabricating smart materials with the ability of […]
Secure communication with light particles that sidesteps the reliance on polarization
Phys.org May 25, 2022 Researchers in Germany have created a scalable star-shaped quantum-key-distribution (QKD) optical-fiber network using WDM of broadband photon pairs to establish key exchange between multiple pairs of participants. They demonstrated simultaneous bipartite key exchange between any possible combination of participants and showed that the quantum bit error rate (QBER) itself can be used to stabilize the phase in the interferometers by small temperature adjustments. The key distribution is insensitive to polarization fluctuations in the network, enabling key distribution using deployed fibers even under challenging environmental conditions. They demonstrated that the network could be extended to 34 participants […]
Chinese team breaks distance record for quantum secure direct communication
Phys.org April 20, 2022 Researchers in China have designed an elaborate physical system and protocol with much enhanced performance for quantum secure communication. The design increased the secrecy capacity greatly by achieving an ultra-low quantum bit error rate of <0.1%, one order of magnitude smaller than that of existing systems. Compared to previous systems, the proposed scheme used photonic time-bin and phase states, operating at 50 MHz of repetition rate, which can be easily upgraded to over 1 GHz using current on-the-shelf technology. Their experiments demonstrated that the proposed system could tolerate more channel loss, from 5.1 dB, which is about 28.3 km in […]
New quantum dots for quantum networks
Phys.org April 7, 2022 Spin can be also used as the medium for quantum communication by transferring quantum information with light. But the process of transferring information to the spin of extremely small electrons is challenging and must be performed efficiently. An international team of researchers (Japan, Canada, Germany) has realized the world’s first GaAs gate-controlled quantum dot circuit on a (110)-oriented surface that promises to increase photon-electron spin conversion efficiency. This has the effect of encoding quantum information from incident photons into the electron spins. Because of the way the hole interacts with the GaAs crystal lattice, the g-factor, […]
Single-photon source paves the way for practical quantum encryption
Phys.org March 23, 2022 Researchers in Australia have developed an on-demand way to generate photons with high purity in a scalable and portable system that operates at room temperature. They combined hexagonal boron nitride with a hemispherical solid immersion lens, which increases the source’s efficiency by a factor of six. They incorporated the single-photon source into a fully portable device that can perform QKD. They demonstrated that it could produce over ten million single photons per second at room temperature. The streamlined device is easier to use and much smaller than traditional optical table setups allowing the system to be […]
New chip hides wireless messages in plain sight
Science Daily November 23, 2021 Traditional encryption methods are challenging to scale for high-bandwidth, ultralow-latency applications. An alternative approach is to use physical-layer techniques that rely on the physics of signal propagation to incorporate security features without the need for an explicit key exchange. Ensuring security using directional, narrow-beam-like features of mm-wave/THz signals has proven to be vulnerable to passive eavesdroppers. An international team of researchers (USA – Princeton University, China) has developed a space-time modulation approach that ensures security by enforcing loss of information through selective spectral aliasing towards the direction of eavesdroppers, even though the channel can be […]