Measurement of B(D_s+ -> mu+ nu_mu)/B(D_s+ -> phi mu+ nu_mu) and Determination of the Decay Constant f_{D_s}

We have observed $23.2 \pm 6.0_{-0.9}^{+1.0}$ purely-leptonic decays of $D_s^+ -> \mu^+ \nu_\mu$ from a sample of muonic one prong decay events detected in the emulsion target of Fermilab experiment E653. Using the $D_s^+ -> \phi \mu^+ \nu_\mu$ yield measured previously in this experiment, we obtain $B(D_s^+ --> \mu^+ \nu_\mu) / B(D_s^+ --> \phi \mu^+ \nu_\mu) =0.16 \pm 0.06 \pm 0.03$. In addition, we extract the decay constant $f_{D_s}=194 \pm 35 \pm 20 \pm 14 MeV$.Comment: 15 pages including one figur

A two-dimensional array of single-hole quantum dots

Quantum dots fabricated using methods compatible with semiconductor manufacturing are promising for quantum information processing. In order to fully utilize the potential of this platform, scaling quantum dot arrays along two dimensions is a key step. Here, we demonstrate a two-dimensional quantum dot array where each quantum dot is tuned to single-charge occupancy, verified by simultaneous measurements using two integrated radio frequency charge sensors. We achieve this by using planar germanium quantum dots with low disorder and a small effective mass, allowing the incorporation of dedicated barrier gates to control the coupling of the quantum dots. We measure the hole charge filling spectrum and show that we can tune single-hole quantum dots from isolated quantum dots to strongly exchange coupled quantum dots. These results motivate the use of planar germanium quantum dots as building blocks for quantum simulation and computation. QCD/Veldhorst LabQCD/Vandersypen LabBUS/TNO STAFFQCD/Scappucci La

Spin Relaxation Benchmarks and Individual Qubit Addressability for Holes in Quantum Dots

We investigate hole spin relaxation in the single- and multihole regime in a 2 × 2 germanium quantum dot array. We find spin relaxation times T1 as high as 32 and 1.2 ms for quantum dots with single- and five-hole occupations, respectively, setting benchmarks for spin relaxation times for hole quantum dots. Furthermore, we investigate qubit addressability and electric field sensitivity by measuring resonance frequency dependence of each qubit on gate voltages. We can tune the resonance frequency over a large range for both single and multihole qubits, while simultaneously finding that the resonance frequencies are only weakly dependent on neighboring gates. In particular, the five-hole qubit resonance frequency is more than 20 times as sensitive to its corresponding plunger gate. Excellent individual qubit tunability and long spin relaxation times make holes in germanium promising for addressable and high-fidelity spin qubits in dense two-dimensional quantum dot arrays for large-scale quantum information.QCD/Veldhorst LabQuTechQCD/Vandersypen LabBusiness DevelopmentQCD/Scappucci La

Phase flip code with semiconductor spin qubits

The fault-tolerant operation of logical qubits is an important requirement for realizing a universal quantum computer. Spin qubits based on quantum dots have great potential to be scaled to large numbers because of their compatibility with standard semiconductor manufacturing. Here, we show that a quantum error correction code can be implemented using a four-qubit array in germanium. We demonstrate a resonant SWAP gate and by combining controlled-Z and controlled-S−1 gates we construct a Toffoli-like three-qubit gate. We execute a two-qubit phase flip code and find that we can preserve the state of the data qubit by applying a refocusing pulse to the ancilla qubit. In addition, we implement a phase flip code on three qubits, making use of a Toffoli-like gate for the final correction step. Both the quality and quantity of the qubits will require significant improvement to achieve fault-tolerance. However, the capability to implement quantum error correction codes enables co-design development of quantum hardware and software, where codes tailored to the properties of spin qubits and advances in fabrication and operation can now come together to advance semiconductor quantum technology.QCD/Veldhorst LabQCD/Vandersypen LabBUS/TNO STAFFQCD/Terhal GroupQuantum ComputingQCD/Scappucci LabQN/Veldhorst La

Data for Universal quantum logic in hot silicon qubits

Data accompanying the paper Universal quantum logic in hot silicon qubits

Observation of D+ -> rho0(770) mu+ nu

We report the first observation of the Cabibbo disfavored semileptonic decay mode D+ -> rho0(770) mu+ nu, and measure its decay rate relative to the Cabibbo favored mode D+ -> K*0(892) mu+ nu to be Gamma(D+ -> rho0(770) mu+ nu) / Gamma(D+ -> K*0(892) mu+ nu) = 0.044 +0.031 -0.025 (stat.) +/- 0.014 (sys). The results are compared to theoretical predictions and to previous experimental upper limits.Comment: 15 pgs., OKHEP-93-0