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Heat transfer in solids is typically conducted through either electrons or atomic vibrations known as phonons. In a vacuum, heat has long been thought to be transferred by radiation but not by phonons because of the lack of a medium.sup.1. Recent theory, however, has predicted that quantum fluctuations of electromagnetic fields could induce phonon coupling across a vacuum and thereby facilitate heat transfer.sup.2-4. Revealing this unique quantum effect experimentally would bring fundamental insights to quantum thermodynamics.sup.5 and practical implications to thermal management in nanometre-scale technologies.sup.6. Here we experimentally demonstrate heat transfer induced by quantum fluctuations between two objects separated by a vacuum gap. We use nanomechanical systems to realize strong phonon coupling through vacuum fluctuations, and observe the exchange of thermal energy between individual phonon modes. The experimental observation agrees well with our theoretical calculations and is unambiguously distinguished from other effects such as near-field radiation and electrostatic interaction. Our discovery of phonon transport through quantum fluctuations represents a previously unknown mechanism of heat transfer in addition to the conventional conduction, convection and radiation. It paves the way for the exploitation of quantum vacuum in energy transport at the nanoscale. Conventionally, heat transfer occurs by conduction, convection or radiation, but has also been theoretically predicted to occur through quantum fluctuations across a vacuum; this prediction has now been confirmed experimentally., Author(s): King Yan Fong [sup.1] , Hao-Kun Li [sup.1] , Rongkuo Zhao [sup.1] , Sui Yang [sup.1] , Yuan Wang [sup.1] , Xiang Zhang [sup.1] [sup.2] Author Affiliations: (1) Nanoscale [...]

Special quantum states are used in metrology to achieve sensitivities below the limits established by classically behaving states.sup.1,2. In bosonic interferometers, squeezed states.sup.3, number states.sup.4,5 and 'Schrödinger cat' states.sup.5 have been implemented on various platforms and have demonstrated improved measurement precision over interferometers using coherent states.sup.6,7. Another metrologically useful state is an equal superposition of two eigenstates with maximally different energies; this state ideally reaches the full interferometric sensitivity allowed by quantum mechanics.sup.8,9. Here we demonstrate the enhanced sensitivity of these quantum states in the case of a harmonic oscillator. We extend an existing experimental technique.sup.10 to create number states of order up to n = 100 and to generate superpositions of a harmonic oscillator ground state and a number state of the form [Formula omitted] with n up to 18 in the motion of a single trapped ion. Although experimental imperfections prevent us from reaching the ideal Heisenberg limit, we observe enhanced sensitivity to changes in the frequency of the mechanical oscillator. This sensitivity initially increases linearly with n and reaches a maximum at n = 12, where we observe a metrological enhancement of 6.4(4) decibels (the uncertainty is one standard deviation of the mean) compared to an ideal measurement on a coherent state with the same average occupation number. Such measurements should provide improved characterization of motional decoherence, which is an important source of error in quantum information processing with trapped ions.sup.11,12. It should also be possible to use the quantum advantage from number-state superpositions to achieve precision measurements in other harmonic oscillator systems. Number-state superpositions of the harmonic motion of a trapped beryllium ion are used to measure the oscillation frequency with quantum-enhanced sensitivity, achieving a mode-frequency uncertainty of about 10.sup.-6., Author(s): Katherine C. McCormick [sup.1] [sup.2] , Jonas Keller [sup.1] , Shaun C. Burd [sup.1] [sup.2] , David J. Wineland [sup.1] [sup.2] [sup.3] , Andrew C. Wilson [sup.1] , Dietrich [...]

Atomic clocks known as optical clocks are more accurate and stable than current timekeepers. Two quantum-engineering approaches could improve the performance of optical clocks even further and extend their applications. Advances in developing a new generation of highly accurate clocks., Author(s): Christian Lisdat, Carsten Klempt Author Affiliations: Quantum engineering for optical clocks Today's most accurate clocks mark the passage of time using transitions of electrons between two energy states in [...]

QUANTUM MODELING FOR HIGH-ENTROPY ALLOYS Materials researchers at the DOE's Ames Laboratory, Iowa, recently identified the source of strength and ductility in high-entropy alloys (HEAs), along with ways to tune [...]

Control of quantum particles has been extended to enable different types of ion to be entangled--correlated in a non-classical way. This opens up opportunities for the development of new quantum [...]

A property called entanglement entropy helps to describe the quantum states of interacting particles, and it has at last been measured. The findings open the door to a deeper understanding [...]