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An object hidden below ground has been located using quantum technology — a long-awaited milestone with profound implications for industry, human knowledge, and national security.

University of Birmingham researchers from the UK National Quantum Technology Hub in Sensors and Timing have reported their achievement in Nature. It is the first in the world for a quantum gravity gradiometer outside of laboratory conditions.

The quantum gravity gradiometer, which was developed under a contract for the Ministry of Defence and in the UKRI-funded Gravity Pioneer project, was used to find a tunnel buried outdoors in real-world conditions one meter below the ground surface. It wins an international race to take the technology outside.

Poli imagines using quantum gravity sensors to monitor groundwater or magma beneath volcanoes, or to help archaeologists uncover hidden tombs or other artifacts without having to dig them up (SN: 11/2/17). These devices could also help farmers check soil quality or help engineers inspect potential construction sites for unstable ground.

“There are many tools to measure gravity,” says Xuejian Wu, an atomic physicist at Rutgers University in Newark, N.J., who wasn’t involved in the study. Some devices measure how far gravity pulls down a mass hanging from a spring. Other tools use lasers to clock how fast an object tumbles down a vacuum chamber. But free-falling atoms, like those in quantum gravity sensors, are the most pristine, reliable test masses out there, Wu says. As a result, quantum sensors promise to be more accurate and stable in the long run than other gravity probes.

Rice University lab manipulates ultracold Rydberg atoms to mimic quantum interactions.

Our spatial sense doesn’t extend beyond the familiar three dimensions, but that doesn’t stop scientists from playing with whatever lies beyond.

Rice University physicists are pushing spatial boundaries in new experiments. They’ve learned to control electrons in gigantic Rydberg atoms with such precision they can create “synthetic dimensions,” important tools for quantum simulations.

Quantum theory was originally formulated using complex numbers. Nonetheless, when replying to a letter by Hendrik Lorenz, Erwin Schrödinger (one of its founding fathers), wrote: “Using complex numbers in quantum theory is unpleasant and should be objected to. The wave function is surely fundamentally a real function.”

In recent years, scientists successfully ruled out any local hidden variable explanation of quantum theory using Bell tests. Later, such tests were generalized to a network with multiple independent hidden variables. In such a quantum network, quantum theory with only real numbers, or “real quantum theory,” and standard quantum theory make quantitatively different predictions in some scenarios, enabling experimental tests of the validity of real quantum theory.

Researchers at Southern University of Science and Technology in China, the Austrian Academy of Sciences and other institutes worldwide have recently adapted one of these tests so that they could be implemented in state-of-the-art photonic systems. Their paper, published in Physical Review Letters, experimentally demonstrates the existence of quantum correlations in an optical network that cannot be explained by real quantum theory.

Radio-Frequency Pulse Enables Association of Triatomic Molecules in Ultracold ²³ Na⁴⁰ K + ⁴⁰ K Gas.

Three-body system is already formidable in classical physics, not to mention the quantum state three-body system. But what if scientists can synthesize triatomic molecules under quantum constraints? It could serve as an appropriate platform to study three-body potential energy surface which is important but difficult to calculate.

Recently, Prof. PAN Jianwei and Prof. ZHAO Bo from the University of Science and Technology of China (USTC), collaborating with Prof. BAI Chunli from Institute of Chemistry of the Chinese Academy of Sciences, found strong evidence for association of triatomic molecules after applying a radio-frequency (rf) pulse to an ultracold mixture of ²³ Na⁴⁰ K and ⁴⁰ K near Feshbach resonance. The work was published in the journal Nature.

Quantum mechanics tells us that the forces of nature come in discrete, tiny chunks. Gravity, the bending of space-time, is a force. So is space-time quantized as well?

This looks interesting.

If it can detect underground structures, not only might it detect tunnels, but it might make tunneling easier.

An object hidden below ground has been located using quantum technology—a long-awaited milestone with profound implications for industry, human knowledge and national security.

Continue reading “Sensor breakthrough paves way for groundbreaking map of world under Earth surface” »

A professor of physics explains how mind-bending quantum experiments are blurring the line between past, present and future. Further, he argues, these experiments, which factor in ‘the relevance of the future to the present’, may demand a radical rethinking of quantum experimentation itself.

Cartography could be changing forever as an advanced tool moves from the lab to the real world. A new quantum gravity sensor helps overcome an issue raised by Einstein.