Tunable coupling scheme for flux qubits at the optimal point

We discuss a practical design for tunably coupling a pair of flux qubits via the quantum inductance of a third high-frequency qubit. The design is particularly well suited for realizing a recently proposed microwave-induced parametric coupling scheme. This is attractive because the qubits can always remain at their optimal points. Furthermore, we will show that the resulting coupling also has an optimal point where it is insensitive to low-frequency flux noise. This is an important feature for the coherence of coupled qubits. The presented scheme is an experimentally realistic way of carrying out two-qubit gates and should be easily extended to multiqubit systems.Comment: 8 pages, 6 figures, minor change

Quantum noise in the Josephson charge qubit

We study decoherence of the Josephson charge qubit by measuring energy relaxation and dephasing with help of the single-shot readout. We found that the dominant energy relaxation process is a spontaneous emission induced by quantum noise coupled to the charge degree of freedom. Spectral density of the noise at high frequencies is roughly proportional to the qubit excitation energy.Comment: Submitted to Phys. Rev. Letter

Decoherence of flux qubits due to 1/f flux noise

We have investigated decoherence in Josephson-junction flux qubits. Based on the measurements of decoherence at various bias conditions, we discriminate contributions of different noise sources. In particular, we present a Gaussian decay function of the echo signal as evidence of dephasing due to $1/f$ flux noise whose spectral density is evaluated to be about $(10^{-6} \Phi_0)^2$/Hz at 1 Hz. We also demonstrate that at an optimal bias condition where the noise sources are well decoupled the coherence observed in the echo measurement is mainly limited by energy relaxation of the qubit.Comment: 4 pages, error in Fig.4 corrected, to appear in PR

Parity effect in superconducting aluminum single electron transistors with spatial gap profile controlled by film thickness

We propose a novel method for suppression of quasiparticle poisoning in Al Coulomb blockade devices. The method is based on creation of a proper energy gap profile along the device. In contrast to the previously used techniques, the energy gap is controlled by the film thickness. Our transport measurements confirm that the quasiparticle poisoning is suppressed and clear 2$e$ periodicity is observed only when the island is made much thinner than the leads. This result is consistent with the existing model and provides a simple method to suppress quasiparticle poisoning

Electromagnetically induced transparency on a single artificial atom

We present experimental observation of electromagnetically induced transparency (EIT) on a single macroscopic artificial "atom" (superconducting quantum system) coupled to open 1D space of a transmission line. Unlike in a optical media with many atoms, the single atom EIT in 1D space is revealed in suppression of reflection of electromagnetic waves, rather than absorption. The observed almost 100 % modulation of the reflection and transmission of propagating microwaves demonstrates full controllability of individual artificial atoms and a possibility to manipulate the atomic states. The system can be used as a switchable mirror of microwaves and opens a good perspective for its applications in photonic quantum information processing and other fields

Ultimate on-chip quantum amplifier

We report amplification of electromagnetic waves by a single artificial atom in open 1D space. Our three-level artificial atom -- a superconducting quantum circuit -- coupled to a transmission line presents an analog of a natural atom in open space. The system is the most fundamental quantum amplifier whose gain is limited by a spontaneous emission mechanism. The noise performance is determined by the quantum noise revealed in the spectrum of spontaneous emission, also characterized in our experiments.Comment: 4 pages, 4 figures + supplemenntary materials accepted for publication in Phys. Rev. Lett

Temperature square dependence of the low frequency 1/f charge noise in the Josephson junction qubits

To verify the hypothesis about the common origin of the low frequency 1/f noise and the quantum f noise recently measured in the Josephson charge qubits, we study temperature dependence of the 1/f noise and decay of coherent oscillations. T^2 dependence of the 1/f noise is experimentally demonstrated, which supports the hypothesis. We also show that dephasing in the Josephson charge qubits off the electrostatic energy degeneracy point is consistently explained by the same low frequency 1/f noise that is observed in the transport measurements.Comment: 4 pages, 2 figure

Proximal phalanx shaft fracture with entrapment in the transverse retinacular ligament: a case report

We report the interesting case of a 33 years old male who underwent operative intervention for a left oblique proximal phalanx shaft fracture of the third finger which penetrated the transverse retinacular ligament (TRL). This patient required operative intervention due to entrapment of the bony fragment in the TRL which acted as a noose with traction on the fractured segment. The fracture was irreducible through a closed maneuver. The use of a dorsal approach allowed visualization of the fracture site and implementation of screws for fixation was deemed adequate secondary to the patient’s bone quality. He was placed in a volar splint at the conclusion of the case to allow for immobilization and protection of the repair. At follow-up, the patient’s radiographic images appeared appropriate and was progressing as expected. We report lessons learned from this case and describe a previously unreported fracture pattern and a possible method of reduction and fixation through a surgical approach in this report

Salter-Harris type II fracture of the middle phalanx with concomitant central slip injury in an 11 year old: a case report

An 11-year-old male sustained an irreducible, completely displaced epiphyseal fracture of the proximal interphalangeal joint (PIPJ) of the middle finger with an associated central slip injury. Central slip injuries occurring in conjunction with Salter-Harris type II middle phalanx fracture are rare entities, with no previously documented case. Our patient underwent open reduction, internal fixation through crossed-pins to achieve reduction and fixation. He was then splinted in extension for six weeks to allow healing of the central slip injury. At 1-year follow-up, the patient had full range-of-motion with no clinical indication of physeal disruption or growth arrest of the repaired digit. We demonstrate a case in which ephiphyseal fractures of the proximal interphalangeal joint with a concomitant central slip injury can safely be treated with open reduction internal fixation combined with a period of immobilization. We characterize a surgical method of reduction and fixation with splinted immobilization and describe lessons learned from this previously unreported case