Characterizing quantum dynamics with initial system-environment correlations.

We fully characterize the reduced dynamics of an open quantum system initially correlated with its environment. Using a photonic qubit coupled to a simulated environment, we tomographically reconstruct a superchannel-a generalized channel that treats preparation procedures as inputs-from measurement of the system alone. We introduce novel quantitative measures for determining the strength of initial correlations, and to allow an experiment to be optimized in regard to its environment.

Experimental distribution of entanglement with separable carriers.

The key requirement for quantum networking is the distribution of entanglement between nodes. Surprisingly, entanglement can be generated across a network without direct transfer-or communication-of entanglement. In contrast to information gain, which cannot exceed the communicated information, the entanglement gain is bounded by the communicated quantum discord, a more general measure of quantum correlation that includes but is not limited to entanglement. Here, we experimentally entangle two communicating parties sharing three initially separable photonic qubits by exchange of a carrier photon that is unentangled with either party at all times. We show that distributing entanglement with separable carriers is resilient to noise and in some cases becomes the only way of distributing entanglement through noisy environments.

Reducing multi-photon rates in pulsed down-conversion by temporal multiplexing.

We present a simple technique to reduce the emission rate of higher-order photon events from pulsed spontaneous parametric down-conversion. The technique uses extra-cavity control over a mode locked ultrafast laser to simultaneously increase repetition rate and reduce the energy of each pulse from the pump beam. We apply our scheme to a photonic quantum gate, showing improvements in the non-classical interference visibility for 2-photon and 4-photon experiments, and in the quantum-gate fidelity and entangled state production in the 2-photon case.

Efficient measurement of quantum dynamics via compressive sensing.

The resources required to characterize the dynamics of engineered quantum systems--such as quantum computers and quantum sensors--grow exponentially with system size. Here we adapt techniques from compressive sensing to exponentially reduce the experimental configurations required for quantum process tomography. Our method is applicable to processes that are nearly sparse in a certain basis and can be implemented using only single-body preparations and measurements. We perform efficient, high-fidelity estimation of process matrices of a photonic two-qubit logic gate. The database is obtained under various decoherence strengths. Our technique is both accurate and noise robust, thus removing a key roadblock to the development and scaling of quantum technologies.

Discrete single-photon quantum walks with tunable decoherence.

Quantum walks have a host of applications, ranging from quantum computing to the simulation of biological systems. We present an intrinsically stable, deterministic implementation of discrete quantum walks with single photons in space. The number of optical elements required scales linearly with the number of steps. We measure walks with up to 6 steps and explore the quantum-to-classical transition by introducing tunable decoherence. Finally, we also investigate the effect of absorbing boundaries and show that decoherence significantly affects the probability of absorption.

Discrete tunable color entanglement.

Although frequency multiplexing of information has revolutionized the field of classical communications, the color degree of freedom (DOF) has been used relatively little for quantum applications. We experimentally demonstrate a new hybrid quantum gate that transfers polarization entanglement of nondegenerate photons onto the color DOF. We create, for the first time, high-quality, discretely color-entangled states (with energy band gap up to 8.4 THz) without any spectrally selective filtering, and unambiguously verify and quantify the amount of entanglement (tangle, 0.611 +/- 0.009) by reconstructing a restricted density matrix; we generate a range of maximally entangled states, including a set of mutually unbiased bases for an encoded qubit space. The technique can be generalized to transfer polarization entanglement onto other photonic DOFs, like orbital angular momentum.

Distributing entanglement and single photons through an intra-city, free-space quantum channel.

We have distributed entangled photons directly through the atmosphere to a receiver station 7.8 km away over the city of Vienna, Austria at night. Detection of one photon from our entangled pairs constitutes a triggered single photon source from the sender. With no direct time-stable connection, the two stations found coincidence counts in the detection events by calculating the cross-correlation of locally-recorded time stamps shared over a public internet channel. For this experiment, our quantum channel was maintained for a total of 40 minutes during which time a coincidence lock found approximately 60000 coincident detection events. The polarization correlations in those events yielded a Bell parameter, S=2.27+/-0.019, which violates the CHSH-Bell inequality by 14 standard deviations. This result is promising for entanglement-based freespace quantum communication in high-density urban areas. It is also encouraging for optical quantum communication between ground stations and satellites since the length of our free-space link exceeds the atmospheric equivalent.

Practical quantum key distribution with polarization entangled photons.

We present an entangled-state quantum cryptography system that operated for the first time in a real-world application scenario. The full key generation protocol was performed in real-time between two distributed embedded hardware devices, which were connected by 1.45 km of optical fiber, installed for this experiment in the Vienna sewage system. The generated quantum key was immediately handed over and used by a secure communication application.

[Critical evaluation of phytothermotherapy ("hay baths") in degenerative arthropathies]. / Valutazione critica del trattamento fitotermoterapico ("bagni di fieno") nelle artropatie degenerative.

It is a traditional practice of the Alpine region of Trentino and Alto Adige to use phytothermotherapeutic treatment with fermenting grass ("hay baths") for chronic degenerative arthropathies. A marked lack of clinical validation is however to be found in current literature as to its efficacy and tolerability. To verify these two aspects 27 patients (mean age 59 +/- 8.7 years, range 43-82) with osteoarthritis (15 of them with a generalized form) were evaluated before and after a ten-day treatment with immersion of the whole body in a bed made with fermenting grass according to the traditional method. The following clinical features were considered: pain in affected joints evaluated by visual analog scale, presence of global subjective improvement (or lack of it) immediately and 6 months after treatment, degree of global functional impairment, stiffness duration, handgrip strength. The mean score at the affected joints (on the visual analog pain scale) was 2.51 +/- 0.71 before and 1.83 +/- 0.89 after treatment (p < 0.001), with improvement in 68% of patients. Morning stiffness was reduced from 38.9 +/- 30.5 to 17.5 +/- 17.2 minutes (p < 0.05), with improvement in 57% of patients. Grip strength measure went from 136 +/- 59.7 to 147 +/- 51 mmHg (p < 0.01), with improvement in 77% of patients. Forty-eight percent of the patients were reassigned to better class of functional capacity (p < 0.001). Patient general assessment signaled improvement in 72% of cases immediately after treatment, and in 80% after six months. Tolerability was high in 23 out of 25 patients, nobody was taken off treatment because of side effects, in two cases a one day interval due to asthenia was introduced. In conclusion, improvement rates were found higher when compared with controlled trials on efficacy of nonsteroidal antiinflammatory drugs. Noteworthy is also the persistence of improvement 6 months after treatment compared to the above mentioned drugs and usual physiokinesitherapeutic treatments.

[Arterial hypertension and hyporeninemic hypoaldosteronism. Description of a clinical case]. / Ipertensione arteriosa ed ipoaldosteronismo iporeninemico. Descrizione di un caso clinico.

In a clinical case of arterial hypertension with hypopotassiaemia and hyporeninaemic hypoaldosteronism due to the use of a dermatological cream containing 9-alpha-fluoroprednisolone, late identification of the iatrogenic cause forced attention on the differential diagnosis of the less frequent hyporeninaemic hypoaldosteronism.