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Category: quantum physics – Page 273

Researchers are claiming a breakthrough in quantum communications, thanks to a new diamond-stretching technique they say greatly increases the temperatures at which qubits remain entangled, while also making them microwave-controllable.

Quantum networking is an emerging field that uses weird quantum phenomena to send and receive information. These networks will be impossible to hack, and will use quantum entanglement to cover large distances, creating pairs of qubits which mirror each other’s quantum state without any physical connection.

Diamond-based qubits are capable of maintaining their state of entanglement for a decent length of time – but only provided they’re kept incredibly cold – just a hair above absolute zero. That limits their usefulness, because it’d mean you’d need a giant, energy-intensive cooling apparatus at every node of your quantum network.

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A future quantum network may become less of a stretch thanks to researchers at the University of Chicago, Argonne National Laboratory and Cambridge University.

A team of researchers announced a breakthrough in quantum network engineering. By “stretching” thin films of diamond, they created that can operate with significantly reduced equipment and expense. The change also makes the bits easier to control.

The researchers hope the findings, published Nov. 29 in Physical Review X, can make future quantum networks more feasible.

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More stable clocks could measure quantum phenomena, including the presence of dark matter.

The practice of keeping time relies on stable oscillations. In grandfather clocks, the length of a second is marked by a single swing of the pendulum. In digital watches, the vibrations of a quartz crystal mark much smaller fractions of time. And in atomic clocks, the world’s state-of-the-art timekeepers, the oscillations of a laser beam stimulate atoms to vibrate at 9.2 billion times per second. These smallest, most stable divisions of time set the timing for today’s satellite communications, GPS systems, and financial markets.

A clock’s stability depends on the noise in its environment. A slight wind can throw a pendulum’s swing out of sync. And heat can disrupt the oscillations of atoms in an atomic clock. Eliminating such environmental effects can improve a clock’s precision. But only by so much.

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Chinese researchers report the successful quantum storage of entangled photons at telecom wavelengths within a crystal, in a breakthrough achievement that reportedly lasted 387 times longer than past similar experiments.

The research team, based at Nanjing University, says their findings could potentially “pave the way for realizing quantum networks based on solid-state devices.”

The Coming Quantum Internet

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In case you missed it, China’s e-commerce giant Alibaba has shut down its quantum computing research effort. It’s not entirely clear what drove the change. Reuters’ reported earlier this week that Alibaba “cut a quantum computing laboratory and team from its research arm, donating both the lab and related experimental equipment to Zhejiang University.”

Alibaba was a relatively early entrant among giant e-commerce/cloud providers into quantum computing research, placing the effort in its Alibaba’s DAMO Academy research organization. There are reports it had invested on the order of $15 billion in the effort. According to the Reuters report, about 30 employees are being released with and effort under way to find positions for them at Zhejiang.

Rather than being tied to specific issues with the quantum research, the prevailing opinion seems to be that the quantum work was caught in the larger turmoil surrounding Alibaba and its ongoing reorganization. The company said its DAMO organization will deepen its work on AI and machining learning research which may be able to have a nearer-term impact on Alibaba’s business.

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Researchers from the University of Ottawa (uOttawa), in collaboration with the Weizmann Institute of Science and Lancaster University, have observed a hidden quantum transition that can only be seen depending on how observers perform measurements.

The study “Topological Transitions of the generalized Pancharatnam-Berry phase” was published in Science Advances on 24 November 2023.

An essential part of the scientific method relies on the ability to measure the output of an experiment accurately and to juxtapose these findings with previous results. Scientists develop measurement devices, or meters, which enable them to precisely quantify the magnitude of physical properties. However, the “measurement process” raises a critical and intriguing question: does the process of measuring a parameter alter the system being measured?

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Entanglement is a quantum phenomenon where the properties of two or more particles become interconnected in such a way that one cannot assign a definite state to each individual particle anymore. Rather, we have to consider all particles at once that share a certain state. The entanglement of the particles ultimately determines the properties of a material.

“Entanglement of many particles is the feature that makes the difference,” says Christian Kokail, one of the first authors of the paper published in Nature. “At the same time, however, it is very difficult to determine.”

The researchers led by Peter Zoller at the University of Innsbruck and the Institute of Quantum Optics and Quantum Information (IQOQI) of the Austrian Academy of Sciences (ÖAW) now provide a new approach that can significantly improve the study and understanding of entanglement in .

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Quantum technologies are currently maturing at a breath-taking pace. These technologies exploit principles of quantum mechanics in suitably engineered systems, with bright prospects such as boosting computational efficiencies or communication security well beyond what is possible with devices based on today’s ‘classical’ technologies.

As with classical devices, however, to realize their full potential, must be networked. In principle, this can be done using the fiber-optic networks employed for classical telecommunications. But practical implementation requires that the information encoded in can be reliably stored at the frequencies used in telecom networks—a capability that has not yet been fully demonstrated.

Writing in Nature Communications, the group of Prof. Xiao-Song Ma at Nanjing University reports record-long quantum storage at telecom wavelengths on a platform that can be deployed in extended networks, paving the way for practical large-scale quantum networks.

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