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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 [...]

Among those who make a living from the science of secrecy, worry and paranoia are just signs of professionalism. Can we protect our secrets against those who wield superior technological powers? Can we trust those who provide us with tools for protection? Can we even trust ourselves, our own freedom of choice? Recent developments in quantum cryptography show that some of these questions can be addressed and discussed in precise and operational terms, suggesting that privacy is indeed possible under surprisingly weak assumptions., Edgar Allan Poe, an American writer and an amateur cryptographer, once wrote '... it may be roundly asserted that human ingenuity cannot concoct a cipher which human ingenuity cannot resolve [...]

Teleportation has been implemented using liquid state nuclear magnetic resonance (NMR) on an ensemble of trichloroethylene (TCE) molecules. The projective measurement step in the standard description of teleportation is modified, while still preserving the teleportation effect. A method based on the two-part Brassard and colleagues method for implementing the Bell basis measurement was used.

A nanometre-scale superconducting electrode linked to a reservoir by a Josephson junction is a single-Cooper-pair box. Quantum oscillations in a single-Cooper-pair box have been observed. A short voltage pulse via a gate electrode controls the coherent quantum state evolution, and modifies the energies of the two charge states. The result superposition of the two charge states is detected by a tunnelling current.

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 [...]

Coherent quantum control is a method of influencing the outcome of a quantum-mechanical interaction. Two-photon transitions in caesium were controlled by using ultrashort pulse-shaping techniques to tailor a femtosecond laser pulse.The cancellation of the transitions is due to destructive quantum interference. Extensive modifications to the pulse shape can be made without having an affect on the two-photon transition probability.

The electrons of metals structured on nanometre length scales are subject to confinement effects governed by Friedel oscillations, and Rudermann-Kittel-Kasuya Yosida oscillations. Quantum oscillations have been detected in a three-dimensional confined electron gas. This was achieved through the insertion of a thin ferromagnetic cobalt film, inducing total spin polarization in the conduction electrons of the copper.

Quantum cryptography using quantum mechanical processes to establish decryption keys allows detection of eavesdropping during message transmission due to an unavoidable and detectable disturbance in the received key information when there is eavesdropping. The use of quantum mechanical processes will allow a single controller on the network to establish and regularly update a distinct secret key with each network user. The keys can then be used to encrypt conventional data transmissions that are sent over the network.

A cost-effective architecture for quantum cryptography has been demonstrated in which a single receiver positioned at a network-hub node is shared by many end users to exchange secret encryption keys. [...]

Quantum mechanics is the most accurate theory of modern physics. It was originally formulated (1) in 1925 to describe microscopic particles such as electrons and atoms, but whether the theory [...]

One of the most fascinating journeys in science concerns the evolution of the description of space and time. Examples of milestones on this journey are the realization that time is [...]

Weinacht and colleagues have described an experiment whereby an atomic electron's wavefunction was shaped and driven into a chosen state with the use of tailored laser pulses. This could have significant applications in quantum computing and bond-selective chemistry. A variant of quantum state holography was used to measure the quantum state of the electron, which relies on interference between the object and the reference wave.

Emanuel Knill and colleagues of Los Alamos National Laboratory have shown that quantum computers can achieve arbitrarily high reliability as long as it is properly design and its components work within a specified tolerance. Quantum computers process information encoded in quantum states, and, in principle, it can solve certain hard problems much faster than other digital devices. Knill and colleagues have analyzed a more general and realistic class of error model, and the principles of fault tolerance could be adapted to realistic laboratory situations.

Quantum cryptography is the first practical application of the foundations of quantum mechanics. In the development of the science of quantum information, new capabilities have been predicted that make use of quantum mechanical superpositions of information. Using quantum key distribution, shared cryptographic key material whose security is assured by the laws of quantum mechanics can be created. However, unanticipated advances in fields like quantum computation could render quantum cryptography not just insecure but also retroactively vulnerable.

The string theory enhances understanding of the quantum properties of black holes. The theory is unique because it enables unification of quantum mechanics and general relativity that are basic for understanding the laws of nature. The calculations, describing the quantum gravity effects of black holes with appropriate magnetic and electric charges, are based on collections of superstrings. These computations reveal that black holes follow the standard principles of quantum mechanics.

The operations of quantum computers are discussed. Quantum mechanics is commonly associated with the uncertainty principle. However, quantum effects within a computer can be used to arrive quickly and with complete certainty at solutions to problems that ordinary computers can arrive at slowly and with a small margin of error. The extra power of quantum computers is derived form the ability of a quantum system to be at many places at the same time when it is not being observed. A discussion of how the interference among different computational paths produces a final output is presented.

Sometimes a scientific idea falls into obscurity as researchers turn their attention elsewhere, yet contains such mathematical beauty that it is revived again and again. Such is the story of [...]

Quantum cryptography, or the use of quantum mechanics to ensure the secrecy of communications, can be realized by using the interference of very dim light pulses as a key distribution. This distribution permits two parties to receive the same random series of numbers, called the key, with near certainty that no one else has received it. Charles Bennett of IBM Research devised an apparatus for producing a code based on a choice between two non-orthogonal states of a quantum system. The uncertainty principle of quantum mechanics keeps unauthorized persons from receiving the code without disclosing themselves.