Experimental Realization of Nonunitary Multiqubit Operations

We demonstrate a novel experimental tool set that enables irreversible multiqubit operations on a quantum platform. To exemplify our approach, we realize two elementary nonunitary operations: the or and nor gates. The electronic states of two trapped ^{40}Ca^{+} ions encode the logical information, and a cotrapped ^{88}Sr^{+} ion provides the irreversibility of the gate by a dissipation channel through sideband cooling. We measure 87% and 81% success rates for the or and nor gates, respectively. The presented methods are a stepping stone toward other nonunitary operations such as in quantum error correction and quantum machine learning.

Phonon Laser in the Quantum Regime

We demonstrate a trapped-ion system with two competing dissipation channels, implemented independently on two ion species cotrapped in a Paul trap. By controlling coherent spin-oscillator couplings and optical pumping rates we explore the phase diagram of this system, which exhibits a regime analogous to that of a (phonon) laser but operates close to the quantum ground state with an average phonon number of n[over ¯]<10. We demonstrate phase locking of the oscillator to an additional resonant drive, and also observe the phase diffusion of the resulting state under dissipation by reconstructing the quantum state from a measurement of the characteristic function.

Generation of a Maximally Entangled State Using Collective Optical Pumping

We propose and implement a novel scheme for dissipatively pumping two qubits into a singlet Bell state. The method relies on a process of collective optical pumping to an excited level, to which all states apart from the singlet are coupled. We apply the method to deterministically entangle two trapped ^{40}Ca^{+} ions. Within 16 pumping cycles, an initially separable state is transformed into one with 83(1)% singlet fidelity, and states with initial fidelity of ⪆70% converge onto a fidelity of 93(1)%. We theoretically analyze the performance and error susceptibility of the scheme and find it to be insensitive to a large class of experimentally relevant noise sources.

Dissipative quantum error correction and application to quantum sensing with trapped ions

Quantum-enhanced measurements hold the promise to improve high-precision sensing ranging from the definition of time standards to the determination of fundamental constants of nature. However, quantum sensors lose their sensitivity in the presence of noise. To protect them, the use of quantum error-correcting codes has been proposed. Trapped ions are an excellent technological platform for both quantum sensing and quantum error correction. Here we present a quantum error correction scheme that harnesses dissipation to stabilize a trapped-ion qubit. In our approach, always-on couplings to an engineered environment protect the qubit against spin-flips or phase-flips. Our dissipative error correction scheme operates in a continuous manner without the need to perform measurements or feedback operations. We show that the resulting enhanced coherence time translates into a significantly enhanced precision for quantum measurements. Our work constitutes a stepping stone towards the paradigm of self-correcting quantum information processing.

Quantum error correction plays a key role in quantum information and metrology, but generally requires complex gates and measurements sequences. Here, the authors use trapped ions to implement a scheme in which always-on coupling to an engineered environment protects the qubit against errors.

Preparation of Entangled States through Hilbert Space Engineering

We apply laser fields to trapped atomic ions to constrain the quantum dynamics from a simultaneously applied global microwave field to an initial product state and a target entangled state. This approach comes under what has become known in the literature as "quantum Zeno dynamics" and we use it to prepare entangled states of two and three ions. With two trapped ^{9}Be^{+} ions, we obtain Bell state fidelities up to 0.990_{-5}^{+2}; with three ions, a W-state fidelity of 0.910_{-7}^{+4} is obtained. Compared to other methods of producing entanglement in trapped ions, this procedure can be relatively insensitive to certain imperfections such as fluctuations in laser intensity.

Dissipative preparation of entanglement in optical cavities

We propose a novel scheme for the preparation of a maximally entangled state of two atoms in an optical cavity. Starting from an arbitrary initial state, a singlet state is prepared as the unique fixed point of a dissipative quantum dynamical process. In our scheme, cavity decay is no longer undesirable, but plays an integral part in the dynamics. As a result, we get a qualitative improvement in the scaling of the fidelity with the cavity parameters. Our analysis indicates that dissipative state preparation is more than just a new conceptual approach, but can allow for significant improvement as compared to preparation protocols based on coherent unitary dynamics.

Route to attosecond nonlinear spectroscopy

We demonstrate generation of coherent microjoule-scale, low-order harmonic supercontinua in the deep and vacuum ultraviolet (4-9 eV), resulting from the nonlinear transformations of near-single-cycle laser pulses in a gas cell. We show theoretically that their formation is connected to a novel nonlinear regime, holding promise for the generation of powerful deep-UV and vacuum ultraviolet subfemtosecond pulses. Our work opens the route to pump-probe spectroscopy of subfemtosecond-scale valence-shell phenomena in atoms, molecules, and condensed matter.

WS5, a direct target of oncogenic transcription factor Myc, is related to human melanoma glycoprotein genes and has oncogenic potential

We have isolated a gene (WS5) that is specifically expressed at the mRNA and protein level in avian fibroblasts transformed by the v-myc oncogene of avian acute leukemia virus MC29. In a conditional cell transformation system, WS5 gene expression was tightly correlated with v-myc activation. The WS5 gene contains 11 exons, encoding a 733-amino acid protein with a transmembrane region and a polycystic kidney disease (PKD) domain. Near the transcriptional start site, the WS5 promoter contains a cluster of four binding sites for the Myc-Max complex and a binding site for transcription factor C/EBPalpha. Electrophoretic mobility shift assays and chromatin immunoprecipitation showed that Myc, Max and C/EBPalpha bind specifically to these sites. Functional promoter analyses revealed that both the Myc-binding site cluster and the C/EBPalpha-binding site are essential for strong transcriptional activation, and that Myc and C/EBPalpha synergistically activate the WS5 promoter. Ectopic expression of WS5 led to cell transformation documented by anchorage-independent growth. The human melanoma antigen Pmel17, a type I transmembrane glycoprotein, is the mammalian protein with the highest amino acid sequence identity (38%) to WS5. The Pmel17 gene is regulated by the MITF protein, a bHLHZip transcription factor with DNA binding specificities similar to those of Myc/Max. WS5 is also related to human glycoprotein GPNMB expressed in metastatic melanoma cells and implicated in the progression of brain and liver tumors.

[Food allergy in the child: an exploratory study on the impact of the elimination diet on food neophobia]

OBJECTIVES

This study was designed to analyse the impact of an elimination diet in children with food allergy, and its perception by their parents on the later reticence of children to test unknown foods, food neophobia.

METHODS

The degree of food neophobia of children having outgrown their allergy (mean age, 7 years 2 months) was compared to that of a sibling (9 years 5 months) using a standardized scale and a questionnaire of food friendliness. Parents were also asked to fill in a questionnaire on the disease and its burden on the family.

RESULTS

Children having outgrown their allergy are more reluctant to test new foods than their non-allergic brother or sister, as shown by their scoring on the food neophobia scale and the number of unknown foods following the cure of the disease. Two factors increase the level of food neophobia, the distressing effect and the duration of the period elapsed until the diagnosis was made, as well as the distressing effect and the lack of variety in the meal preparation.

CONCLUSION

Food neophobia, a normal phase between 2 and 10 years, is worsened by the elimination diet required by food allergy, especially in case of late diagnosis and when the time elapsed before diagnosis and the preparation of meals were perceived as difficult to bear.

JAC, a direct target of oncogenic transcription factor Jun, is involved in cell transformation and tumorigenesis

Using subtractive hybridization techniques, we have isolated a gene termed JAC that is strongly and specifically activated in avian fibroblasts transformed by the v-jun oncogene of avian sarcoma virus 17 (ASV17), but not in cells transformed by other oncogenic agents. Furthermore, JAC is highly expressed in cell lines derived from jun-induced avian fibrosarcomas. Kinetic analysis using a doxycycline-controlled conditional cell transformation system showed that expression of the 0.8-kb JAC mRNA is induced rapidly upon activation of the oncogenic v-jun allele. Nucleotide sequence analysis and transcriptional mapping revealed that the JAC gene contains two exons, with the longest ORF confined to exon 2. The deduced 68-amino acid chicken JAC protein is rich in cysteine residues and displays 37% sequence identity to mammalian high-sulfur keratin-associated proteins. The promoter region of JAC contains a consensus (5'-TGACTCA-3') and a nonconsensus (5'-TGAGTAA-3') AP-1 binding site in tandem, which are both specifically bound by the Gag-Jun hybrid protein encoded by ASV17. Mutational analysis revealed that the two AP-1 sites confer strong transcriptional activation by Gag-Jun in a synergistic manner. Ectopic expression of JAC in avian fibroblasts leads to anchorage-independent growth, strongly suggesting that deregulation of JAC is an essential event in jun-induced cell transformation and tumorigenesis.

Post-stroke spasticity management with repeated botulinum toxin injections in the upper limb

OBJECTIVE

Although the botulinum toxin A (BTX-A) treatment has proved effective in spasticity management, no information is available with regard to the effects of repeated injections over time.

DESIGN

To evaluate the effects of BTX-A on moderate or severe upper limb spasticity, an exploratory investigation was performed on 28 stroke patients treated for 2 yr or longer and observed for 3 yr. Every 3 to 5 mo, each patient received BTX-A injections in upper limb muscles. The assessment, performed before and 1 mo after each injection for a median of 28 mo, included technical and functional objectives and the burden of care. The former were evaluated by using the modified Ashworth Scale for spasticity and the goniometric measurement of rest position and range of motion; functional objectives were evaluated by means of the Frenchay Arm Test and a patient/caregiver goals assessment scale.

RESULTS

BTX-A treatment was followed by an improvement in all technical outcome measures. Motor dexterity scores improved in only 8 of 28 patients, vs. daily living activities, which increased in all subjects. Although the average dosage injected per session did not change, intervals between injections became longer. No relationship between either spasticity onset or residual motoricity and response to treatment could be found.

CONCLUSIONS

This investigation is relevant clinically because repeated BTX-A injections show unchanging effectiveness in the management of focal spasticity after stroke.

Immediate effects of therapeutic facilitation on the gait of hemiparetic patients as compared with walking with and without a cane

OBJECTIVES

Although the neurodevelopmental technique (Bobath) is the most widely used approach in the gait rehabilitation of hemiparetic subjects in Europe, there is little neurophysiological evidence for its presumed effects on gait symmetry and facilitation of paretic muscles during the therapeutic intervention. The study, therefore, investigated the immediate effects of gait entrainment by a physical therapist on the gait of hemiparetic subjects.

METHODS

Cycle parameters, gait symmetry, hip joint movement and the electromyographic activity of several lower limb muscles were assessed in 22 patients during a classic intervention by five Bobath therapists and while walking with and without a cane.

RESULTS

Multivariate statistics revealed that, while being assisted by the therapist, patients walked faster (P = 0.022), with a longer relative stance period of the affected leg (P = 0.005), a higher symmetry (P = 0.002), larger hip extension (P = 0.001) and more activation (P = 0.026) of the Mm. triceps surae, vastus lateralis, biceps femoris and gluteus medius as compared to walking with and without a cane. Extensor spasticity of the plantar-flexor tended to increase (n.s.). In five subjects, no after-effect could be documented 1 h after a gait training of 30 min.

CONCLUSIONS

The study confirmed a more balanced walking pattern in conjunction with facilitation of various weight bearing muscles during the therapeutic intervention. A prolonged single stance period of the affected leg, an unobstructed hip movement, enhanced weight acceptance and a faster gait seemed to be responsible for the observed immediate effects of the therapeutic intervention.

Botulinum toxin type A and short-term electrical stimulation in the treatment of upper limb flexor spasticity after stroke: a randomized, double-blind, placebo-controlled trial

OBJECTIVE

To investigate whether the combined approach of botulinum toxin type A (BtxA) and electrical stimulation was more effective than the toxin alone in the treatment of chronic upper limb spasticity after stroke.

DESIGN

Randomized, placebo-controlled study with four treatment groups: 1000 units BtxA (Dysport) + electrical stimulation (A), 1000 units BtxA (B), placebo + electrical stimulation (C) and placebo (D).

SETTING

A neurological rehabilitation clinic.

SUBJECTS

Twenty-four stroke patients with chronic upper limb spasticity after stroke, six patients in each treatment group.

INTERVENTIONS

Intramuscular injection of either toxin or placebo into six upper imb flexor muscles. In group A and C additional electrical stimulation of the injected muscles with surface electrodes, three times half an hour each day for three days.

MAIN OUTCOME MEASURES

Muscle tone rated with the modified Ashworth score, limb position at rest and difficulties encountered during three upper limb motor tasks assessed before and 2, 6 and 12 weeks after injection.

RESULTS

Most improvements were observed in patients of group A. Cleaning the palm (p = 0.004) differed across groups. Pairwise comparison for this target variable showed that group A differed from group B and D (p <0.01), but not from C. Indicative across-group differences were obtained for elbow spasticity reduction (p = 0.011), and improvement of putting the arm through a sleeve (p = 0.020).

CONCLUSIONS

The placebo-controlled trial favours the concept that electrical stimulation enhances the effectiveness of BtxA in the treatment of chronic upper limb flexor spasticity after stroke.

Low-dose botulinum toxin with ankle taping for the treatment of spastic equinovarus foot after stroke

OBJECTIVE

To evaluate the efficacy of a combined treatment for spastic foot using selective injections of botulinum toxin (BTA) into the tibialis posterior muscle followed by ankle taping, and to compare it with current BTA treatment procedure.

DESIGN

Single-blind randomized control trial. Three-month follow-up after treatment.

SETTING

Neurorehabilitation clinic.

SUBJECTS

Eighteen outpatients with equinovarus foot due to severe spasticity after stroke.

INTERVENTIONS

(1) Injection of 190 to 320 BTA U into several calf muscles (group A); (2) injection of 100 BTA U into the tibialis posterior muscle, followed by ankle-foot taping (group B).

MAIN OUTCOME MEASURES

Ankle range of motion (ROM), Ashworth scale, gait velocity, and step length.

RESULTS

Average Ashworth scores decreased 1 point in both groups, but the benefit appeared of shorter duration in group B. Changes in both foot position at rest and passive ankle ROM were observed in all patients, without treatment-related differences, except for gain in passive dorsiflexion that appeared higher in group A. Gait velocity and step length showed similar increases in both groups.

CONCLUSION

The combination of selective injections of low BTA doses with ankle-foot taping is as effective as the injection of the current doses for the reduction of foot inversion with positive effects on gait parameters.

[Development of a gait trainer with regulated servo-drive for rehabilitation of locomotor disabled patients]

The aim of the present study was to develop a new gait trainer for the rehabilitation of non-ambulatory patients. For the simulation of the gait phase, we used a commercially available fitness trainer (Fast Track) with two foot plates moving in an alternating fashion and connected to a servo-controlled propulsion system providing the necessary support for the movement depending on the patient's impairment level. To compensate deficient equilibrium reflexes, the patient was suspended in a harness capable of supporting some of his/her weight. Video analysis of gait and the kinesiological EMG were used to assess the pattern of movement and the corresponding muscle activity, which were then evaluated in healthy subjects, spinal cord injured and stroke patients and compared with walking on the flat or on a treadmill. Walking on the gait trainer was characterised by a symmetrical, sinusoidal movement of lower amplitude than in normal gait. The EMG showed a low activity of the tibialis anterior muscle, while the antigravity muscles were clearly activated by the gait trainer during the stance phase. In summary, the new gait trainer generates a symmetrical gait-like movement, promoting weight acceptance in the stance phase, which is important for the restoration of walking ability.

Asymmetry of gait initiation in hemiparetic stroke subjects

OBJECTIVE

To investigate symmetry of gait initiation in healthy and hemiparetic subjects.

DESIGN

Survey.

SETTING

Kinematic laboratory affiliated with a hospital-based department of rehabilitation.

PATIENTS OR OTHER PARTICIPANTS

Ten healthy and 14 hemiparetic stroke subjects starting five times with their right and left leg, respectively.

MAIN OUTCOME MEASURES

Duration of defined periods, step length, center of pressure, and center of mass were recorded and calculated using two triaxial force plates, contact switches, and a video camera system.

RESULTS

Healthy subjects displayed a high degree of independence of kinetic and kinematic parameters of the starting limb. Hemiparetic patients showed differences with respect to the starting limb: when starting with the nonaffected leg, the swing period and step length was shorter and the center of pressure displayed a more marked medio-lateral sway with no corresponding initial movement of the center of mass; when starting with the affected leg the movement pattern of the center of pressure and center of mass was comparable to that of normal subjects.

CONCLUSIONS

The trajectories of the center of pressure and center of mass and the symmetry parameters are in accordance with a higher degree of uncertainty when starting with the non-affected limb in hemiparetic subjects.

Gait initiation, development of a measuring device for use in a clinical environment

Gait initiation is a part of daily mobility, its restoration thus plays a major role in the rehabilitation of hemiparetic patients that have a higher risk of falling. This study presents a clinically applicable system for the analysis of gait initiation of healthy persons and hemiparetic patients. For this purpose we have analysed the triaxial ground reaction forces yielding the displacement of the centre of pressure (CP) and, with a two-fold integration of ground reaction forces, the centre of mass (CM). These are descriptive parameters of the dynamics and symmetry of gait initiation that could predict the risk of falling. Hemiparetic patients showed a distinct behaviour when starting either with their affected or non-affected limb. Future applications include individual assessment of patients with gait disabilities and validation of physiotherapy strategies.

[Long-term therapy of oligozoospermia with the aromatase inhibitor testolactone]

In a pilot study, 13 subfertile men with idiopathic normogonadotropic oligozoospermia were treated by the aromatase inhibitor testolactone for a period of 6 months. During the administration of 1 g testolactone daily, a significant increase in the sperm count, total sperm output and the absolute number of motile and progressively motile spermatozoa was observed 3 and 6 months after the initiation of therapy, but there were no significant changes in the percentage of motile and progressively motile spermatozoa, sperm morphology or ejaculate volume. The serum hormone levels of testosterone, LH, FSH and oestradiol were assessed before and during testolactone administration; there was a significant increase of testosterone and FSH after 1 and 3 months of treatment, but LH levels increased only during the 1st month of therapy. The oestradiol level showed a significant decrease, while the increase in testosterone/oestradiol ratio was more than twice as expected. The pregnancy rate was 17%. No severe side-effects were reported during testolactone therapy. The results of the study support the hypothesis that oestrogens are involved in the regulation of human spermatogenesis.