quantum_mechanics (3)

Left, schematics of the apparatus (positron beam, collimators, SiN gratings and emulsion detector. A HpGe detector is used as beam monitor). Right, single-particle interference visibility as a function of the positron energy is in agreement with quantum mechanics (blue) and disagrees with classical physics (orange dashed). Courtesy: Politecnico di Milano


Topics: Antimatter, High Energy Physics, Particle Physics, Quantum Mechanics

Researchers in Italy and Switzerland have performed the first ever double-slit-like experiment on antimatter using a Talbot-Lau interferometer and a positron beam.

The classic double-slit experiment confirmed that light and matter have the characteristics of both waves and particles, a duality that was first put forward by de Broglie in 1923. This superposition principle is one of the main postulates of quantum mechanics and researchers have since been able to diffract and interfere matter waves of objects of increasing complexity – from electrons to neutrons and molecules.

The QUPLAS (QUantum Interferometry and Gravitation with Positrons and LAsers) collaboration, which includes researchers from the Politecnico di Milano L-NESS in Como, the Milan unit of the Istituto Nazionale di Fisica Nucleare (INFN), the Università degli Studi di Milano and the University of Bern, has now performed the first interference experiment on positrons – the antimatter equivalent of electrons.

“The experiment was first proposed for electrons by Albert Einstein and Richard Feynman as a thought experiment and realized by Merli, Missiroli and Pozzi in 1976 and more systematically by Tonomura and colleagues in 1989,” explains QUPLAS spokesman Marco Giammarchi of the INFN. “In this original experiment, which was voted by Physics World as the most beautiful experiment, the researchers demonstrated the specifically quantum effect of single particle interference, which – according to Feynman – is the central ‘mystery’ of quantum theory.”


Antimatter quantum interferometry makes its debut, Belle Dumé, Physics World

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Quantum Robustness...

A study demonstrates that a combination of two materials, aluminum and indium arsenide, forming a device called a Josephson junction could make quantum bits more resilient. Credit: University of Copenhagen image/Antonio Fornieri


Topics: Computer Science, Quantum Computing, Quantum Mechanics

Researchers have been trying for many years to build a quantum computer that industry could scale up, but the building blocks of quantum computing, qubits, still aren't robust enough to handle the noisy environment of what would be a quantum computer.

A theory developed only two years ago proposed a way to make qubits more resilient through combining a semiconductor, indium arsenide, with a superconductor, aluminum, into a planar device. Now, this theory has received experimental support in a device that could also aid the scaling of qubits.

This semiconductor-superconductor combination creates a state of "topological superconductivity," which would protect against even slight changes in a qubit's environment that interfere with its quantum nature, a renowned problem called "decoherence."

The device is potentially scalable because of its flat "planar" surface – a platform that industry already uses in the form of silicon wafers for building classical microprocessors.

The work, published in Nature, was led by the Microsoft Quantum lab at the University of Copenhagen's Niels Bohr Institute, which fabricated and measured the device. The Microsoft Quantum lab at Purdue University grew the semiconductor-superconductor heterostructure using a technique called molecular beam epitaxy, and performed initial characterization measurements.


New robust device may scale up quantum tech, researchers say, Kayla Wiles, Purdue University

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Super State...

Super state: three independent groups have caught sight of supersolidity. (Courtesy: iStock/3quarks)


Topics: Bose-Einstein Condensate, Condensed Matter Physics, Electromagnetism, Quantum Mechanics

Atomic systems that behave very much like supersolids have been created independently by teams of physicists in Italy, Germany have Austria. The teams have shown that dipolar quantum gases trapped by magnetic fields can spontaneously separate into arrays of coherent droplets, providing a system closer to the original conception of a supersolid.

The supersolid phase is a counterintuitive quantum state of matter that has both crystalline order and frictionless flow at very low temperatures. The phenomenon is related to superfluidity and was predicted 50 years ago by Soviet physicists Alexander Andreev and Ilya Lifschitz. However, supersolidity has proved frustratingly difficult to observe.

In a superfluid, the energy required to create a density modulation generally increases as the modulation’s wavelength gets shorter. At one characteristic wavelength, however, the energy takes a sudden dip – much as waves pass more easily through a crystal when the wavelength equals the separation between the atoms. If the superfluid were cold enough, Andreev and Lifschitz reasoned, the energy required would drop to zero at this wavelength. The superfluid would then spontaneously separate into tiny droplets, effectively forming an ordered crystal.


Supersolid behavior spotted in dipolar quantum gases, Tim Wogan, Physics World

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