Abstract We propose an autonomous quantum error correction scheme using squeezed cat (SC) code against excitation loss in continuous-variable systems. Through reservoir engineering, we show that a structured dissipation can stabilize two-component SC while autonomously correcting the errors. The implementation of such only requires low-order nonlinear couplings among three bosonic modes or between mode and qutrit. While our proposed is device independent, it readily implementable with...

We propose an architecture of quantum-error-correction-based quantum repeaters that combines techniques used in discrete- and continuous-variable information. Specifically, we to encode the transmitted qubits a concatenated code consisting two levels. On first level use GKP encoding qubit single bosonic mode. second small discrete-variable code. Such has important features. Firstly, errors on each levels are corrected different types. This enables for achieving performance needed practical...

Stabilized cat codes can provide a biased noise channel with set of bias-preserving (BP) gates, which significantly reduce the resource overhead for fault-tolerant quantum computing. All existing schemes BP however, require adiabatic evolution, performance limited by excitation loss and nonadiabatic errors during gates. In this paper, we apply derivative-based leakage-suppression technique to overcome errors, so that implement fast gates on Kerr-cat qubits improved gate fidelity while...

Protected qubits such as the 0-π qubit, and bosonic including cat Gottesman-Kitaev-Preskill (GKP) offer advantages for fault tolerance. Some of these protected (e.g., qubit Kerr-cat qubit) are stabilized by Hamiltonians which have (near-)degenerate ground state manifolds with large energy gaps to excited manifolds. Without dissipative stabilization mechanisms performance energy-gap-protected can be limited leakage states. Here, we propose a scheme dissipatively stabilizing an using colored...

Quantum error correction (QEC) for generic errors is challenging due to the demanding threshold and resource requirements. Interestingly, when physical noise biased, we can tailor our QEC schemes improve performance. Here study a family of codes having XZZX-type stabilizer generators, including set cyclic generalized from five-qubit code topological that call toric (GTCs). We show these XZZX are highly qubit efficient if tailored biased noise. To characterize performance, use notion...

We present a fault-tolerant Bell-pair distillation scheme achieving constant overhead through high-rate quantum low-density parity-check (qLDPC) codes. Our approach maintains rate equal to the code - as high $1/3$ in our implementations while requiring no additional beyond physical qubits of code. Full circuit-level analysis demonstrates fault-tolerance for input Bell pair infidelities below threshold $\sim 5\%$, readily achievable with near-term capabilities. Unlike previous proposals,...

Quantum error correction holds the key to scaling up quantum computers. Cosmic ray events severely impact operation of a computer by causing chip-level catastrophic errors, essentially erasing information encoded in chip. Here, we present distributed scheme combat devastating effect such introducing an additional layer erasure correcting code across separate chips. We show that our is fault tolerant against errors and discuss its experimental implementation using superconducting qubits with...

The response of quantum-conductance-based hydrogen sensors fabricated by controllable deposition closely spaced Pd nanoparticle films between interdigital electrodes was investigated. Three typical regions with different conductance–hydrogen pressure correlations were observed. characteristics the devices found to depend strongly on coverage. In low H2 region, higher coverage gives sensitivity. high quantitative sensing can only be realized Optimizing allows attainment highly sensitive a...

Bosonic qubits encoded in continuous-variable systems provide a promising alternative to two-level for quantum computation and communication. So far, photon loss has been the dominant source of errors bosonic qubits, but significant reduction recent qubit experiments suggests that dephasing should also be considered. However, detailed understanding combined channel is lacking. Here, we show that, unlike its constituent parts, loss-dephasing non-degradable, pointing towards richer structure...

Quantum low-density parity-check (qLDPC) codes can achieve high encoding rates and good code distance scaling, providing a promising route to low-overhead fault-tolerant quantum computing. However, the long-range connectivity required implement such makes their physical realization challenging. Here, we propose hardware-efficient scheme perform computation with high-rate qLDPC on reconfigurable atom arrays, directly compatible recently demonstrated experimental capabilities. Our approach...

An efficient state estimation model, neural network (NNE), empowered by machine learning techniques, is presented for full quantum tomography (FQST). A parameterized function based on applied to map the measurement outcomes estimated states. Parameters are updated with supervised procedures. From computational complexity perspective our algorithm most one among existing algorithms tomography. We perform numerical tests prove both accuracy and scalability of model.

Fault-tolerant quantum computation with bosonic qubits often necessitates the use of noisy discrete-variable ancillae. In this work, we establish a comprehensive and practical fault-tolerance framework for such hybrid system synthesize it fault-tolerant protocols by combining error correction (QEC) advanced control techniques. We introduce essential building blocks error-corrected gadgets leveraging ancilla-assisted operations using generalized variant path-independent control. Using these...

We study the nonlinear behaviors of mass-spring systems damped by dry friction using simulation a LC circuit anti-parallel diodes. show that differential equation for electric oscillator is equivalent to mechanical system when piecewise linear model used simplify diodes' I–V curve. derive series solutions under weak approximation which can describe resonant response as well amplitudes superharmonic components. The experimental results are consistent with solutions. also present phenomenon...

Stabilized cat qubits that possess biased noise channel with bit-flip errors exponentially smaller than phase-flip errors. Together a set of bias-preserving (BP) gates, are promising candidate for realizing hardware efficient quantum error correction and fault-tolerant computing. Compared to dissipatively stabilized qubits, the Kerr can in principle support faster gate operations higher fidelity, benefiting from large energy gap protects code space. However, leakage cats increase minor type...

Fault-tolerant quantum computation with depolarization error often requires demanding threshold and resource overhead. If the operations can maintain high noise bias -- dominated by dephasing small bit-flip we achieve hardware-efficient fault-tolerant a more favorable threshold. Distinct from two-level physical systems, multi-level systems (such as harmonic oscillators) desirable set of bias-preserving while using continuous engineered dissipation or Hamiltonian protection to stabilize...

We propose to learn a generative model via entropy interpolation with Schrödinger Bridge. The learning task can be formulated as interpolating between reference distribution and target based on the Kullback-Leibler divergence. At population level, this is characterized an SDE $[0,1]$ time-varying drift term. sample we derive our Bridge algorithm by plugging term estimated deep score estimator density ratio into Euler-Maruyama method. Under some mild smoothness assumptions of distribution,...

Quantum error correction is necessary to perform large-scale quantum computation, but requires extremely large overheads in both space and time. High-rate low-density-parity-check (qLDPC) codes promise a route reduce qubit numbers, performing computation while maintaining low cost has required serialization of operations extra time costs. In this work, we design fast parallelizable logical gates for qLDPC codes, demonstrate their utility key algorithmic subroutines such as the adder. Our...

We present a biased atomic qubit, universally implementable across all platforms, encoded as `spin-cat' within ground state Zeeman levels. The key characteristic of our configuration is the coupling spin manifold size $F_g \gg 1$ to an excited $F_e = F_g - using light. This results in eigenstates driven atom that include exactly two dark states manifold, which are decoupled from light and immune spontaneous emission states. These constitute `spin-cat', leading designation `dark spin-cat'....

We report a theoretical study of the simultaneous high-efficiency, equal-level outputs second and third harmonics in quasiperiodic optical superlattice at any given fundamental intensity. The principle is that nonlinear coupling effectively controlled by introducing proper quasiphase mismatches, use tunability linear refractive index gratings induced applying dc electric field based on electro-optic effect. results verify this approach feasible very efficient. In addition, we also make...