Lifeboat Foundation

Decoherence is the bane of quantum technologies. In coherent systems, the phase of the wave functions representing the quantum states of particles in the system have definite relations between each other. This allows quantum devices to operate in a meaningful way that differs from classical devices. However, interacting with the world around us rapidly leads to decoherence, which makes it harder to exploit quantum effects for enhancing computation efficiency or communication security. Research has shown that quantum systems with impressively long coherence times are possible in diamond, but diamond is far from the favorite for manufacturers. Now, researchers at the University of Science and Technology in Hefei and Wuhan University in China have demonstrated SiC can boast some of the quantum merits of diamond with the additional advantage of optical control at the wavelengths used by the telecommunications industry.

The defects prized for quantum technologies are nitrogen-vacancy (NV) centers, in which a carbon atom in diamond is replaced by a nitrogen with a missing carbon at the neighboring crystal lattice site. What makes this kind of defect interesting for quantum technologies is that you can control its quantum spin states with light and produce photon-spin entanglement with long coherence times, even at room temperature. The difficulties arise when trying to position the technology in the real world as opposed to the lab. The photon-spin interactions for NV centers in diamond need light at visible wavelengths—telecommunications wavelengths are much longer. In addition, these finely engineered devices need to be hacked out of one of the hardest (and most expensive) materials known to man, one that industry does not have established nanofabrication protocols for.

It turns out there are types of defects in SiC that might also be useful for quantum technologies. SiC is widely used in power electronics, so commercially viable avenues for producing SiC devices already exist. Over the past 10 years, vacancies and divacancies (where one or a pair of atoms in the lattice are absent) in SiC began to attract interest when researchers learned that they could also control their spin states with light at room temperature with long coherence times. The observation of NV centers in SiC really piqued interest, as these were optically active at the wavelengths used by the telecommunications industry as opposed to the shorter visible wavelengths needed to control the spin states of vacancies and divacancies in SiC.

The standard formulation of quantum theory relies on a fixed space-time metric determining the localisation and causal order of events. In general relativity, the metric is influenced by matter, and is expected to become indefinite when matter behaves quantum mechanically. Here, we develop a framework to operationally define events and their localisation with respect to a quantum clock reference frame, also in the presence of gravitating quantum systems. We find that, when clocks interact gravitationally, the time localisability of events becomes relative, depending on the reference frame. This relativity ia a signature of an indefinite metric, where events can occur in an indefinite causal order. Even if the metric is indefinite, for any event we can find a reference frame where local quantum operations take their standard unitary dilation form. This form is preserved when changing clock reference frames, yielding physics covariant with respect to quantum reference frame transformations.

As far back as 2015, the National Institute of Standards and Technology (NIST) began asking encryption experts to submit their candidate algorithms for testing against quantum computing’s expected capabilities — so this is an issue that has already been front of mind for security professionals and organizations. But even with an organization like NIST leading the way, working through all those algorithms to judge their suitability to the task will take time. Thankfully, others within the scientific community have also risen to the challenge and joined in the research.

It will take years for a consensus to coalesce around the most suitable algorithms. That’s similar to the amount of time it took ECC encryption to gain mainstream acceptance, which seems like a fair comparison. The good news is that such a timeframe still should leave the opportunity to arrive at — and widely deploy — quantum-resistant cryptography before quantum computers capable of sustaining the number of qubits necessary to seriously threaten RSA and ECC encryption become available to potential attackers.

The ongoing development of quantum-resistant encryption will be fascinating to watch, and security professionals will be sure to keep a close eye on which algorithms and encryption strategies ultimately prove most effective. The world of encryption is changing more quickly than ever, and it has never been more important for the organizations dependent on that encryption to ensure that their partners are staying ahead of the curve.

Anyons – the particle-like collective excitations that can exist in some 2D materials – tend to bunch together in a two-dimensional conductor. This behaviour, which has now been observed by physicists at the Laboratory of Physics of the ENS (LPENS) and the Center for Nanoscience and Nanotechnologies (C2N) in Paris, France, is completely different to that of electrons, and experimental evidence for it is important both for fundamental physics and for the potential future development of devices based on these exotic quasiparticles.

The everyday three-dimensional world contains two types of elementary particles: fermions and bosons. Fermions, such as electrons, obey the Pauli exclusion principle, meaning that no two fermions can ever occupy the same quantum state. This tendency to flee from each other is at the heart of a wide range of phenomena, including the electronic structure of atoms, the stability of neutron stars and the difference between metals (which conduct electric current) and insulators (which don’t). Bosons such as photons, on the other hand, tend to bunch together – a gregarious behaviour that gives rise to superfluid and superconducting behaviours when many bosons exist in the same quantum state.

Within the framework of quantum mechanics, fermions also differ from bosons in that they have antisymmetric wavefunctions – meaning that a minus sign (that is, a phase φ equal to π) is introduced whenever two fermions are exchanged. Bosons, in contrast, have symmetric wavefunctions that remain the same when two bosons are exchanged (φ=0).

We report terahertz (THz) light-induced second harmonic generation, in superconductors with inversion symmetry that forbid even-order nonlinearities. The THz second harmonic emission vanishes above the superconductor critical temperature and arises from precession of twisted Anderson pseudospins at a multicycle, THz driving frequency that is not allowed by equilibrium symmetry. We explain the microscopic physics by a dynamical symmetry breaking principle at sub-THz-cycle by using quantum kinetic modeling of the interplay between strong THz-lightwave nonlinearity and pulse propagation. The resulting nonzero integrated pulse area inside the superconductor leads to light-induced nonlinear supercurrents due to subcycle Cooper pair acceleration, in contrast to dc-biased superconductors, which can be controlled by the band structure and THz driving field below the superconducting gap.

Researchers at the University of Science and Technology of China have recently introduced a new satellite-based quantum-secure time transfer (QSTT) protocol that could enable more secure communications between different satellites or other technology in space. Their protocol, presented in a paper published in Nature Physics, is based on two-way quantum key distribution in free space, a technique to encrypt communications between different devices.

“Our main idea was to realize quantum-secure time transfer in order to resolve the security issues in practical time–frequency transfer,” Feihu Xu, one of the researchers who carried out the study, told Phys.org.

Quantum key distribution (QKD) is a technique to achieve secure communication that utilize cryptographic protocols based on the laws of quantum mechanics. Quantum key distribution protocols can generate secret security keys based on quantum physics, enabling more secure data transfer between different devices by spotting attackers who are trying to intercept communications.

Essentially a quantum radar teleportation device could entangle objects anywhere in the universe.

Last year, a Long March 2D rocket took off from the Jiuquan Satellite Launch Centre in the Gobi Desert carrying a satellite called Micius, named after an ancient Chinese philosopher who died in 391 B.C. The rocket placed Micius in a Sun-synchronous orbit so that it passes over the same point on Earth at the same time each day.

Micius is a highly sensitive photon receiver that can detect the quantum states of single photons fired from the ground. That’s important because it should allow scientists to test the technological building blocks for various quantum feats such as entanglement, cryptography, and teleportation.

Continue reading “First Object Teleported from Earth to Orbit” »

Cesium atoms and laser traps offer a more robust type of quantum computer.

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