Hamiltonian Engineering with Multicolor Drives for Fast Entangling Gates and Quantum Crosstalk Cancellation.

Quantum computers built with superconducting artificial atoms already stretch the limits of their classical counterparts. While the lowest energy states of these artificial atoms serve as the qubit basis, the higher levels are responsible for both a host of attractive gate schemes as well as generating undesired interactions. In particular, when coupling these atoms to generate entanglement, the higher levels cause shifts in the computational levels that lead to unwanted ZZ quantum crosstalk. Here, we present a novel technique to manipulate the energy levels and mitigate this crosstalk with simultaneous off-resonant drives on coupled qubits. This breaks a fundamental deadlock between qubit-qubit coupling and crosstalk. In a fixed-frequency transmon architecture with strong coupling and crosstalk cancellation, additional cross-resonance drives enable a 90 ns CNOT with a gate error of (0.19±0.02)%, while a second set of off-resonant drives enables a novel CZ gate. Furthermore, we show a definitive improvement in circuit performance with crosstalk cancellation over seven qubits, demonstrating the scalability of the technique. This Letter paves the way for superconducting hardware with faster gates and greatly improved multiqubit circuit fidelities.

Demonstration of a High-Fidelity cnot Gate for Fixed-Frequency Transmons with Engineered ZZ Suppression.

Improving two-qubit gate performance and suppressing cross talk are major, but often competing, challenges to achieving scalable quantum computation. In particular, increasing the coupling to realize faster gates has been intrinsically linked to enhanced cross talk due to unwanted two-qubit terms in the Hamiltonian. Here, we demonstrate a novel coupling architecture for transmon qubits that circumvents the standard relationship between desired and undesired interaction rates. Using two fixed frequency coupling elements to tune the dressed level spacings, we demonstrate an intrinsic suppression of the static ZZ while maintaining large effective coupling rates. Our architecture reveals no observable degradation of qubit coherence (T_{1},T_{2}>100 µs) and, over a factor of 6 improvement in the ratio of desired to undesired coupling. Using the cross-resonance interaction, we demonstrate a 180 ns single-pulse controlled not (cnot) gate, and measure a cnot fidelity of 99.77(2)% from interleaved randomized benchmarking.

Cerebroplacental ratio as a predictor of intrapartum fetal compromise in term pregnancy.

OBJECTIVE: To predict intrapartum fetal compromise (FC) and admission to neonatal intensive care unit (NICU) by cerebroplacental ratio (CPR) in term pregnancies. METHODS: A prospective observational study recruited women with singleton, term pregnancies. Ultrasound (US) was done for fetal biometry, umbilical and middle cerebral artery (UA, MCA) Doppler parameters, and CPR calculated. Intrapartum variables and neonatal data were recorded. RESULTS: Mean interval from US to delivery was 2.21 ± 2.71 days. Rate of operative delivery for FC was 17.47%. Multivariate logistic regression analysis showed that UA pulsatility index (PI) multiples of median (MoM) (P = 0.001), MCA PI MoM (P = 0.001), and CPR MoM (P = 0.001) were significantly and independently associated with operative delivery for FC. Similarly, UA PI MoM (P = 0.004), MCA PI MoM (P = 0.009), and CPR MoM (P = 0.003) were also significantly and independently associated with admission to the NICU. Rate of operative delivery for presumed FC was higher in approprate-for-gestational-age fetuses with low CPR than in small-for-gestational-age fetuses with normal CPR (43.1% and 37.5%, respectively). CONCLUSION: Lower mean CPR and CPR MoM were independently associated with the need for operative delivery for presumed FC and NICU admission at term. CPR is more likely to be associated with FC due to placental insufficiency than birth weight.