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We present QSteed, a quantum compilation system that can be deployed on real quantum computing devices and quantum computing clusters. It is designed to meet the challenges of effectively compiling quantum tasks and managing multiple quantum backends. The system integrates two core components: a quantum compiler and a quantum computing resource virtualization manager, both of which provide standardized interfaces. The resource manager models quantum chips into different abstract layers, including the real quantum processing unit (QPU), the standard QPU (StdQPU), the substructure QPU (SubQPU), and the virtual QPU (VQPU), and stores this information in a quantum computing resource virtualization database, thus realizing the unified management of quantum computing devices. The quantum compiler adopts a modular and extensible design, providing a flexible framework for customizing compilation optimization strategies. It provides hardware-aware compilation algorithms that account for quantum gate noise and qubit coupling structures. By selecting the most suitable computing resources from the VQPU library, the compiler maps quantum tasks to the optimal qubit regions of the target device. We validated the effectiveness of the QSteed on the superconducting devices of the Quafu quantum cloud computing cluster. The quantum computing resource virtualization management technology of QSteed and the flexible and extensible design of its compiler make it possible to achieve unified management and task compilation for backend devices of multiple physical systems such as neutral-atom and ion-trap., Comment: White paper for QSteed, with 7 figures and 18 pages

In this paper, the mixed equilibrium problem with coupled inequality constraints in dynamic environments is solved by employing a multi-agent system, where each agent only has access to its own bifunction, its own constraint function, and can only communicate with its immediate neighbors via a time-varying digraph. At each time, the goal of agents is to cooperatively find a point in the constraint set such that the sum of local bifunctions with a free variable is non-negative. Different from existing works, here the bifunctions and the constraint functions are time-varying and only available to agents after decisions are made. To tackle this problem, first, an online distributed algorithm involving accurate gradient information is proposed based on mirror descent algorithms and primal-dual strategies. Of particular interest is that dynamic regrets, whose offline benchmarks are to find the solution at each time, are employed to measure the performance of the algorithm. Under mild assumptions on the graph and the bifunctions, we prove that if the deviation in the solution sequence grows within a certain rate, then both the dynamic regret and the violation of coupled inequality constraints increase sublinearly. Second, considering the case where each agent only has access to a noisy estimate on the accurate gradient, we propose an online distributed algorithm involving the stochastic gradients. The result shows that under the same conditions as in the first case, if the noise distribution satisfies the sub-Gaussian condition, then dynamic regrets, as well as constraint violations, increase sublinearly with high probability. Finally, several simulation examples are presented to corroborate the validity of our results.

The observed timing data, magnetic tilt angle $\chi$, and age of young pulsars could be used to probe some important issues about neutron star (NS) physics, e.g., the NS internal magnetic field configuration, and the number of precession cycles $\xi$. \textbf{Both} quantities are critical in studying the continuous gravitational wave emission from pulsars, and the latter generally characterizes the mutual interactions between superfluid neutrons and other particles in the NS interior. The timing behavior of pulsars can be influenced by the dipole field evolution, which instead of decaying, may increase with time. An increase in the dipole field may result from the re-emergence of the initial dipole field $B_{\rm d,i}$ that was buried into the NS interior shortly after the birth of the NS. In this work, the field re-emergence scenario $\xi$ and the internal field configuration of several young pulsars, as well as their $B_{\rm d, i}$ are investigated by assuming typical accreted masses $\Delta M$. Moreover, since the Crab pulsar has an exactly known age and its tilt angle change rate can be inferred from observations, we can set stringent constraints on its $\xi$, $B_{\rm d,i}$, and $\Delta M$. Although for other young pulsars without exactly known ages and tilt angle change rates, these quantities cannot be accurately determined, we find that their $\xi$ are generally within $\sim10^4-10^6$, and some of them probably have magnetar-strength $B_{\rm d,i}$. Our work could be important for investigating the transient emissions associated with NSs, the origin of strong magnetic fields of NSs, pulsar population, continuous gravitational wave emission from pulsars, and accretion under extreme conditions in principle.

The initial spin periods of newborn magnetars are \textbf{strongly associated with the origin of their strong magnetic fields, both of which can affect the electromagnetic radiation and gravitational waves (GWs) emitted at their birth.} Combining the upper limit $E_{\rm SNR}\lesssim10^{51}$ erg on the explosion energies of \textbf{the supernova (SN) remnants around slowly-spinning magnetars} with a detailed investigation on the evolution of newborn magnetars, we set constraints on the initial spin periods of magnetars \textbf{born in weak SN explosions}. Depending on the conversion efficiency $\eta$ of the electromagnetic energy of \textbf{these} newborn magnetars into the kinetic energy of SN ejecta, the minimum initial spin periods of \textbf{these} newborn magnetars are $P_{\rm i, min}\simeq 5-6$ ms for an ideal efficiency $\eta=1$, $P_{\rm i, min}\simeq 3-4$ ms for a possible efficiency $\eta=0.4$, and $P_{\rm i, min}\simeq 1-2$ ms for a relatively low efficiency $\eta=0.1$. \textbf{Based on these constraints and adopting reasonable values for the physical parameters of the newborn magnetars, we find that their GW radiation at $\nu_{\rm e,1}=\nu$ may be undetectable by the Einstein Telescope (ET) since the maximum signal-to-noise ratio (${\rm S/N}$) is only 2.41 even the sources are located at a very close distance of 5 Mpc, where $\nu$ are the spin frequencies of the magnetars. At such a distance, the GWs emitted at $\nu_{\rm e,2}=2\nu$ from the newborn magnetars with dipole fields $B_{\rm d}=5\times10^{14}$ and $10^{15}$ G may be detectable by the ET because ${\rm S/N}$ are 10.01 and 19.85, respectively. However, if these newborn magnetars are located at $20$ Mpc away in the Virgo supercluster, no GWs could be detected by the ET due to low ${\rm S/N}$.

The observational data (e.g., the timing data and magnetic tilt angles $\chi$) of young pulsars can be used to probe some critical issues about the internal physics of neutron stars (NSs), for instance, the number of precession cycles $\xi$ and the internal magnetic field configuration (IMFC) of NSs. Evolution of the dipole magnetic field $B_{\rm d}$ of NSs may play an important role in determining the final results. In this work, a power-law form is adopted to describe the decay of $B_{\rm d}$. In such a scenario, the IMFC and $\xi$ of young pulsars with an ordinary $B_{\rm d}\sim10^{12}-\-10^{13}$ G and a steady braking index $n$ are investigated. Since the tilt angle change rates $\dot{\chi}$ of pulsars with $n<3$ can be theoretically predicted, a test on the power-law decay model can thus be made by comparing the theoretical values to that obtained from observations. However, such a comparison can only be made on the Crab pulsar currently, and the results show that the power-law decay model is inconsistent with the Crab's observations. We suggest that rather than decay, the Crab's $B_{\rm d}$ should increase with time at a rate $\sim12-14$ G/s. A definite conclusion on the validity of the power-law decay model for pulsars with ordinary $B_{\rm d}$ may be given if $\dot{\chi}$ of other pulsars could be measured.