Physical Review Research

This Perspective outlines a staged road map for building a fault-tolerant quantum computer based on topologically protected Majorana-based qubits. The plan spans several device generations, from a single-qubit device used for qubit benchmarking, a two-qubit device for a measurement-based braiding operation, and an eight-qubit device for quantum error detection to extended qubit lattices that support universal logical operations at scale. Key design elements, operating protocols, and the advantages of this approach for scalable, utility-scale quantum computation are highlighted.

The decay dynamics of nonlinear nanomechanical systems in phase space via two-tone-drive ringdowns is experimentally explored. Linear and nonlinear libration, scattering off saddles, and metastable states near ghosts with nontrivial energy exchange are observed.

It is shown that, in the framework of Hubbard-corrected density-functional theory (DFT + $U$), intersite +$V$ corrections can be recast to first order as a purely on-site correction acting on hybridized Hubbard orbitals. This connects intersite Hubbard corrections to the choice of projectors, highlights inconsistencies in the conventional method for computing $V$, and raises questions about what the Hubbard subspaces fundamentally are.

An analytic expression is derived for the phase of a quantum vortex in a dipolar Bose-Einstein condensate, capturing the anisotropy introduced by the long-range dipole-dipole interactions. Using this phase profile, the dipolar point vortex model is formulated; this model reproduces the anisotropic velocities, deformed orbits, and orientation-dependent motion of vortex pairs found in full numerical simulations of the condensate.

Atom interferometers promise access to the decihertz gravitational-wave band, below LIGO’s reach and above LISA’s, where compact binaries radiate for hours to days before merger. This paper makes the case for building a kilometer-scale vertical atom interferometer in the Antarctic ice at the South Pole, where seismic noise is among the lowest on Earth, hot-water drilling and heavy-cargo logistics have already been proven by IceCube, and the southern location completes global source triangulation. Beyond early-warning alerts for multimessenger follow-up, such an instrument would enable precision tests of the equivalence principle and searches for wavelike dark matter.

A study looks at the conditions under which an adiabatic variational quantum eigensolver succeeds, where approximate ground states generated along an adiabatic path serve as initial states for successive optimization steps. A self-verification procedure based on energy-standard-deviation measurements is introduced that assesses eigenstate accuracy during run-time and verifies convergence to the target ground state.

Rayleigh superradiant scattering is used to probe a dipolar ${}^{166}$Er gas across the crossover from a Bose-Einstein condensate to a macrodroplet. The scattering efficiency peaks near the crossover, and rapid light-induced atom depletion reveals distinct expansion dynamics in each regime and a crossover shift with magnetic field orientation.

A systematic analysis of the resolution-relevance framework tests the possibility to identify informative low-resolution representations from empirical statistics alone in an unsupervised manner. Across synthetic, image-derived, and molecular datasets, increasing dimensionality or informative content progressively improves the method’s ability to select representations that preserve the underlying distribution, tracing the conditions under which data-driven resolution selection provides a faithful low-resolution description.

This article reveals that previous observations, in which the nonequilibrium dynamics of long-range models mirror short-range systems under local quenches, reflect a universal feature of long-range interacting quantum systems. This is demonstrated by showing that this feature is also present under global quenches.

A space-time Floquet operator is introduced that captures the long-time dynamics of systems with intertwined spatial and temporal periodicities. The resulting band framework uncovers fractional quantized charge pumping, connects topological windings to Floquet–Bloch oscillations, and predicts nonreciprocal amplification.

An XOR-FWHT algorithm is presented for the deterministic evaluation of the second-order stabilizer Rényi entropy of generic $N$-qubit pure states represented as full state vectors, reducing the computational cost from 𝒪(8${}^N$) to 𝒪($N$4${}^N$). The method exploits XOR-shifted amplitude correlations and fast Walsh-Hadamard transforms, without relying on sampling or special structure of the input state.

Scanning SQUID current imaging reveals domain-dependent charge transport anisotropy at the (111) LaAlO${}_3$/SrTiO${}_3$ interface and connects it to the nonlinear Hall response. The combined local and global measurements reveal how broken symmetries give rise to anisotropic orbital Rashba coupling and provide an electrical probe of orbital textures.

Single-crystal measurements and numerical calculations reveal a quantum-disordered magnetic ground state in the triangular-lattice magnet CeMgAl${}_{11}$O${}_{19}$, with no magnetic ordering observed down to 30 mK. Quantitative comparison with an anisotropic spin-1/2 model places the material further from the exactly solvable quantum critical point than previously estimated, suggesting that structural disorder may contribute to the suppression of magnetic order.

Universal continuous-variable gate sets are shown to enable fault-tolerant quantum memory. This is achieved via numerical simulation of the generation of Gottesman-Kitaev-Preskill (GKP) states and comparison with the fault-tolerant memory threshold of the GKP surface code.

Rare-earth pyrochlore iridates offer a fertile ground for unconventional magnetic phenomena. In Tb${}_2$Ir${}_2$O${}_7$, the low-temperature magnetic order is particularly unusual, with an additional component orthogonal to the one favored by the predominant interactions. Combining numerical simulations, neutron scattering, and specific heat down to dilution temperatures, this work shows that the quantum nature of Tb${}^{3+}$ ions, subject to rare-earth interactions and to the Ir magnetic field, plays a key role in shaping the magnetic order.

Although polar molecules are promising candidates for quantum computing, entangling gates built with them suffer from fluctuations in the dipole-dipole interaction (DDI). A high-fidelity molecular gate protocol is introduced that uses an exotic spin echo to suppress population in DDI-active states, alongside a theoretical framework revealing that DDI couples to only half of the motional modes during the gate.