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An international team led by researchers at Princeton University has uncovered a new pattern of ordering of electric charge in a novel superconducting material.

The researchers discovered the new type of ordering in a material containing atoms arranged in a peculiar structure known as a kagome lattice. While researchers already understand how the electron’s spin can produce magnetism, these new results provide insights into the fundamental understanding of another type of quantum order, namely, orbital magnetism, which addresses whether the charge can spontaneously flow in a loop and produce magnetism dominated by extended orbital motion of electrons in a lattice of atoms. Such orbital currents can produce unusual quantum effects such as anomalous Hall effects and be a precursor to unconventional superconductivity at relatively high temperatures. The study was published in the journal Nature Materials.

“The discovery of a novel charge order in a kagome superconductor with topological band-structure which is also tuneable via a magnetic field is a major step forward that could unlock new horizons in controlling and harnessing quantum topology and superconductivity for future fundamental physics and next-generation device research,” said M. Zahid Hasan, the Eugene Higgins Professor of Physics at Princeton University, who led the research team.

Circa 2017

The future Internet is very likely the mixture of all-optical Internet with low power consumption and quantum Internet with absolute security. The optical regular Internet would be used by default, but switched over to quantum Internet when sensitive data need to be transmitted. PT and and its counterpart in the quantum limit SPT would be the core components for both OIP and QIP in future Internet. Compared with electronic transistors, PTs/SPTs potentially have higher speed, lower power consumption and compatibility with fibre-optic communication systems.

Several schemes for PT^6,7,8,9,10 and SPT^{11,12,13,14,15,16,17} have been proposed or even proof-of-principle demonstrated. All these prototypes exploit optical nonlinearities, i.e., photon-photon interactions¹⁸. However, photons do not interact with each other intrinsically, so indirect photon-photon interactions via electromagnetically induced transparency (EIT)¹⁹, photon blockade²⁰ and Rydberg blockade²¹ were intensively investigated in this context over last two decades in either natural atoms^22,23 or artificial atoms including superconducting boxes^24,25 and semiconductor quantum dots (QDs)^12,13. PT can seldom work in the quantum limit as SPT with the gain greater than 1 because of two big challenges, i.e., the difficulty to achieve the optical nonlinearities at single-photon levels and the distortion of single-photon pulse shape and inevitable noise produced by these nonlinearities²⁶. The QD-cavity QED system is a promising solid-state platform for information and communication technology (ICT) due to their inherent scalability and matured semiconductor technology. But the photon blockade resulting from the anharmonicity of Jaynes-Cummings energy ladder²⁷ is hard to achieve due to the small ratio of the QD-cavity coupling strength to the system dissipation rates^{12,13,28,29,30,31,32} and the strong QD saturation³³. Moreover, the gain of this type of SPT based on the photon blockade is quite limited and only 2.2 is expected for In(Ga)As QDs^12,13.

Continue reading “Photonic transistor and router using a single quantum-dot-confined spin in a single-sided optical microcavity” »

A new on-chip device that is very good at mediating interactions between light and atoms in a vapour has been developed by researchers in Germany and the UK. Flavie Davidson-Marquis at Humboldt University of Berlin and colleagues call their device a “quantum-optically integrated light cage” and say that it could be used for wide range of applications in quantum information technology.

Hybrid quantum photonics is a rapidly growing area of research that integrates different optical systems within miniaturized devices. One area of interest is the creation of devices for the control, storage and retrieval of the quantum states of light using individual atoms. This is usually done by integrating on-chip photonic devices with miniaturized cells containing warm vapours of alkali atoms. However, this approach faces challenges due to inefficient vapour filling times, high losses of quantum information near cell surfaces and limited overlaps between the wavelengths of light used in optical circuits and the wavelengths of atomic transitions.

Researchers from University of Copenhagen have developed a new technique that keeps quantum bits of light stable at room temperature instead of only working at-270 degrees. Their discovery saves power and money and is a breakthrough in quantum research.

As almost all our private information is digitalized, it is increasingly important that we find ways to protect our data and ourselves from being hacked.

Quantum Cryptography is the researchers’ answer to this problem, and more specifically a certain kind of qubit — consisting of single photons: particles of light.

Cosmic-ray particles and γ-rays striking superconducting circuits can generate qubit errors that are spatially correlated across several millimetres, hampering current error-correction approaches.

Using LIGO’s laser beams to reduce jiggling rather than detect gravitational waves, scientists have gotten closer to the realm of quantum mechanics.

Big Blue has, for the first time, built a quantum computer that is not physically located in its US data centers. For the company, this is the start of global quantum expansion.

Computer model simulates how interactions extend exciton lifetimes.

Given the importance of the Kirkwood–Dirac quasiprobability’s nonclassical values, two natural questions arise: Under what conditions does this quasiprobability behave anomalously? And how anomalous can its behaviour get? That’s what we wanted to explore.

What did you do in the paper?

We pinned down conditions under which the Kirkwood–Dirac quasiprobability assumes nonclassical values. Using these conditions, one can calculate which experiments can exhibit certain types of quantum advantages. We also put a “ceiling” on how much nonclassicality one Kirkwood–Dirac quasiprobability distribution can contain.