Robotics versus laparoscopy - an experimental study of the transfer effect in maiden users

ABSTRACT: BACKGROUND: Robot-assisted laparoscopy (RL) is used in a wide range of operative interventions, but the advantage of this technique over conventional laparoscopy (CL) remains unclear. Studies comparing RL and CL are scarce. The present study was performed to test the hypothesis that maiden users master surgical tasks quicker with the robot-assisted laparoscopy technique than with the conventional laparoscopy technique. METHODS: 20 subjects, with no prior surgical experience, performed three different surgical tasks in a standardized experimental setting, repeated four times with each of the RL and CL techniques. Speed and accuracy were measured. A cross-over technique was used to eliminate gender bias and the experience gained by carrying out the first part of the study. RESULTS: The task "tie a knot" was performed faster with the RL technique than with CL. Furthermore, shorter operating times were observed when changing from CL to RL. There were no time differences for the tasks of grabbing the needle and continuous suturing between the two operating techniques. Gender did not influence the results. CONCLUSION: The more advanced task of tying a knot was performed faster using the RL technique than with CL. Simpler surgical interventions were performed equally fast with either technique. Technical skills acquired during the use of CL were transferred to the RL technique. The lack of tactile feedback in RL seemed to matter. There were no differences between males and females

Quantum nondemolition detection of a propagating microwave photon

The ability to nondestructively detect the presence of a single, traveling photon has been a long-standing goal in optics, with applications in quantum information and measurement. Realising such a detector is complicated by the fact that photon-photon interactions are typically very weak. At microwave frequencies, very strong effective photon-photon interactions in a waveguide have recently been demonstrated. Here we show how this type of interaction can be used to realize a quantum nondemolition measurement of a single propagating microwave photon. The scheme we propose uses a chain of solid-state 3-level systems (transmons), cascaded through circulators which suppress photon backscattering. Our theoretical analysis shows that microwave-photon detection with fidelity around 90% can be realized with existing technologies

Large collective Lamb shift of two distant superconducting artificial atoms

Virtual photons can mediate interaction between atoms, resulting in an energy shift known as a collective Lamb shift. Observing the collective Lamb shift is challenging, since it can be obscured by radiative decay and direct atom-atom interactions. Here, we place two superconducting qubits in a transmission line terminated by a mirror, which suppresses decay. We measure a collective Lamb shift reaching 0.8% of the qubit transition frequency and exceeding the transition linewidth. We also show that the qubits can interact via the transmission line even if one of them does not decay into it.Comment: 7+5 pages, 4+2 figure

Giant Cross Kerr Effect for Propagating Microwaves Induced by an Artificial Atom

We have investigated the cross Kerr phase shift of propagating microwave fields strongly coupled to an artificial atom. The artificial atom is a superconducting transmon qubit in an open transmission line. We demonstrate average phase shifts of 11 degrees per photon between two coherent microwave fields both at the single-photon level. At high control power, we observe phase shifts up to 30 degrees. Our results provide an important step towards quantum gates with propagating photons in the microwave regime.Comment: 5 pages, 4 figure

Leggett-Garg inequality violations with a large ensemble of qubits

We investigate how discrete internal degrees of freedom in a quasimacroscopic system affect the violation of the Leggett-Garg inequality, a test of macroscopic realism based on temporal correlation functions. As a specific example, we focus on an ensemble of qubits subject to collective and individual noise. This generic model can describe a range of physical systems, including atoms in cavities, electron or nuclear spins in nitrogen-vacancy (NV) centers in diamond, erbium in Y2SiO5, bismuth impurities in silicon, or arrays of superconducting circuits, to indicate but a few. Such large ensembles are potentially more macroscopic than other systems that have been used so far for testing the Leggett-Garg inequality and open a route toward probing the boundaries of quantum mechanics at macroscopic scales. We find that, because of the nontrivial internal structure of such an ensemble, the behavior of different measurement schemes, under the influence of noise, can be surprising. We discuss which measurement schemes are optimal for flux qubits and NV centers, and some of the technological constraints and difficulties for observing such violations with present-day experiments

Engineering the Level Structure of a Giant Artificial Atom in Waveguide Quantum Electrodynamics

Engineering light-matter interactions at the quantum level has been central to the pursuit of quantum optics for decades. Traditionally, this has been done by coupling emitters, typically natural atoms and ions, to quantized electromagnetic fields in optical and microwave cavities. In these systems, the emitter is approximated as an idealized dipole, as its physical size is orders of magnitude smaller than the wavelength of light. Recently, artificial atoms made from superconducting circuits have enabled new frontiers in light-matter coupling, including the study of "giant" atoms which cannot be approximated as simple dipoles. Here, we explore a new implementation of a giant artificial atom, formed from a transmon qubit coupled to propagating microwaves at multiple points along an open transmission line. The nature of this coupling allows the qubit radiation field to interfere with itself leading to some striking giant-atom effects. For instance, we observe strong frequency-dependent couplings of the qubit energy levels to the electromagnetic modes of the transmission line. Combined with the ability to in situ tune the qubit energy levels, we show that we can modify the relative coupling rates of multiple qubit transitions by more than an order of magnitude. By doing so, we engineer a metastable excited state, allowing us to operate the giant transmon as an effective lambda system where we clearly demonstrate electromagnetically induced transparency.Comment: 12 pages, 8 figure

Probing the quantum vacuum with an artificial atom in front of a mirror

Quantum fluctuations of the vacuum are both a surprising and fundamental phenomenon of nature. Understood as virtual photons flitting in and out of existence, they still have a very real impact, \emph{e.g.}, in the Casimir effects and the lifetimes of atoms. Engineering vacuum fluctuations is therefore becoming increasingly important to emerging technologies. Here, we shape vacuum fluctuations using a "mirror", creating regions in space where they are suppressed. As we then effectively move an artificial atom in and out of these regions, measuring the atomic lifetime tells us the strength of the fluctuations. The weakest fluctuation strength we observe is 0.02 quanta, a factor of 50 below what would be expected without the mirror, demonstrating that we can hide the atom from the vacuum

Breakdown of the cross-kerr scheme for photon counting

We show, in the context of single-photon detection, that an atomic three-level model for a transmon in a transmission line does not support the predictions of the nonlinear polarizability model known as the cross-Kerr effect.We show that the induced displacement of a probe in the presence or absence of a single photon in the signal field, cannot be resolved above the quantum noise in the probe. This strongly suggests that cross-Kerr media are not suitable for photon counting or related single-photon applications. Our results are presented in the context of a transmon in a one-dimensional microwave waveguide, but the conclusions also apply to optical systems

Quantum Acoustics with Surface Acoustic Waves

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.Comment: 14 pages, 12 figure