Quantum information can be stored in micromechanical resonators, encoded as quanta of vibration known as phonons. The vibrational motion is then restricted to the stationary eigenmodes of the resonator, which thus serves as local storage for phonons. In contrast, we couple propagating phonons to an artificial atom in the quantum regime, and reproduce findings from quantum optics with sound taking over the role of light. Our results highlight the similarities between phonons and photons, but also point to new opportunities arising from the unique features of quantum mechanical sound. The low propagation speed of phonons should enable new dynamic schemes for processing quantum information, and the short wavelength allows regimes of atomic physics to be explored which cannot be reached in photonic systems.The quantum nature of light is revealed and explored in its interaction with atoms, which can be either elemental or artificial. Artificial atoms typically have transition frequencies in the microwave range and can be designed on a microchip with parameters tailored to fit specific requirements. This makes them well suited as tools to investigate fundamental phenomena of atomic physics and quantum optics. In the form of superconducting qubits, they have seen extensive use in closed spaces (electromagnetic cavities), where they have ample time to interact with confined microwave radiation (1-3). These experiments have recently been extended to quantum optics in open one-dimensional (1D) transmission lines, where the atom interacts with itinerant microwave photons (4-7). We present an acoustic equivalent of such a system, where the quantum properties of sound are explored, rather than those of light.At the intersection between quantum informatics and micromechanics, recent milestones include the coupling between a superconducting qubit and a vibrational mode (8,9), hybrids of mechanical resonators and electrical microwave cavities (10), and the use of mechanics to interface between microwaves and optical photons (11,12). The system we present here is another manifestation of mechanics in the quantum regime, but one that differs fundamentally from the suspended resonators mentioned above. In our case, the phonons are not bound to the eigenmodes of any structure, but consist of Surface Acoustic Waves (SAWs) which propagate freely over long distances, before and after interacting with an atom in their path.In the domain of quantum information, SAWs with high power have been used to transport electrons and holes in semiconductors (13)(14)(15). This stands in contrast with our use of SAWs, where the power is much too low to transport charge carriers, and we instead focus on the quantum nature of the phonons themselves.We do this by coupling an artificial atom directly to the SAWs via piezoelectricity, so that this mode of interaction becomes the dominant one for the atom. This means that we can communicate with the atom bidirectionally through the SAW channel, exciting it acoustically as well as listening to its emission...

This study examined psychological and physiological stress, as well as muscle tension and musculoskeletal symptoms, among 72 female supermarket cashiers. Stress levels were found to be significantly elevated at work, as reflected in the catecholamines, blood pressure, heart rate, electromyographic (EMG) activity, and self-reports. Fifty cashiers (70%) suffering from neck-shoulder pain (trapezius myalgia) were found to have higher EMG activity at work and reported more tension after work. Women who kept a diary for 1 week and reported more musculoskeletal pain (above the median) were older, had higher blood pressure, and reported more work stress and psychosomatic symptoms. The elevated stress levels at work are consistent with data from workers involved in other types of repetitive tasks and can be important for the high prevalence of neck and shoulder symptoms among the cashiers.

It has recently been demonstrated that surface acoustic waves (SAWs) can interact with superconducting qubits at the quantum level. SAW resonators in the GHz frequency range have also been found to have low loss at temperatures compatible with superconducting quantum circuits. These advances open up new possibilities to use the phonon degree of freedom to carry quantum information. In this paper, we give a description of the basic SAW components needed to develop quantum circuits, where propagating or localized SAW-phonons are used both to study basic physics and to manipulate quantum information. Using phonons instead of photons offers new possibilities which make these quantum acoustic circuits very interesting. We discuss general considerations for SAW experiments at the quantum level and describe experiments both with SAW resonators and with interaction between SAWs and a qubit. We also discuss several potential future developments.

The conversion efficiency of electric microwave signals into surface acoustic waves in different types of superconducting transducers is studied with the aim of quantum applications. We compare delay lines containing either conventional symmetric transducers (IDTs) or unidirectional transducers (UDTs) at 2.3 GHz and 10 mK. The UDT delay lines improve the insertion loss with 4.7 dB and a directivity of 22 dB is found for each UDT, indicating that 99.4 % of the acoustic power goes in the desired direction. The power lost in the undesired direction accounts for more than 90 % of the total loss in IDT delay lines, but only ∼3 % percent of the total loss in the FEUDT delay lines.Surface acoustic waves (SAWs) are Rayleigh waves propagating on the surface of a solid [1]. It has recently been suggested [2] and shown [3] that SAWs can interact with artificial atoms at the quantum level. This is fundamentally interesting because the artificial atoms can be made much larger than the wavelength of the SAW, which is not possible in other systems [4]. There are extensive new possibilities for quantum devices utilizing SAW; such as resonators [5,6], absorption in double quantum dots [7], transport of quantum information [8][9][10] and phonon assisted tunneling [11].When SAWs are used to carry quantum information, it is important to have low losses. The purpose here is to lower the conversion loss between electric signals (photons) and SAWs (phonons). In all studies about quantum SAW applications, SAWs are converted to and from electric microwave signals using conventional symmetric interdigital transducers (IDTs). The IDT can be described by a three port scattering matrix, where port 1 and 2 are acoustic and port 3 is electric [12]. It has the same electric to SAW conversion in both ports, i.e. S 13 = S 23 , and hence 50 % of the power is converted in the wrong direction. This means that IDTs are limited by a theoretical minimum insertion loss of -3 dB and because of reciprocity delay lines with two IDTs are theoretically limited to -6 dB.Unlike the symmetric IDT, a unidirectional transducer (UDT) [13,14] can be optimized to release most of its SAW energy in one preferred direction, by maximizing the scattering element S 13 while minimizing S 23 . In this way UDTs can exceed the -3 dB loss, and therefore UDTs are interesting to study for quantum SAW applications.