Multiphoton resonances to high-lying energy levels represent an unavoidable source of Floquet heating in strongly driven quantum systems. In this work, we extend the recently developed two-tone approach of “canceling” multiphoton resonances to shaken lattices in the Hubbard regime. Our experiments show that even for strong lattice shaking, the inclusion of a weak second drive leads to cancellation of multiphoton heating resonances. Surprisingly, the optimal canceling amplitude depends on the Hubbard interaction strength $U$, in qualitative agreement with exact diagonalization calculations. Our results call for novel analytical approaches to capture the physics of strongly driven, strongly interacting many-body systems.

We discuss the nonlinear process of backward-wave parametric amplification and oscillation, phase matched using a nonlinear grating inside a chiral medium. Our theory shows a remarkable feature manifesting as photoinduced flipping of optical chirality between the signal and the idler waves, without any change in the structural chirality of the medium. We show that circular birefringence, induced by chirality, leads to two different nonlinear processes with different phase-matching conditions that are associated with opposite states of circular polarizations. When the incident pump and signal beams are linearly polarized initially, their state of polarization evolves in an elliptical fashion because of the two competing nonlinear processes taking place in parallel. We also discuss the properties of such cavityless optical parametric oscillators based on distributed feedback provided by the nonlinear grating used for quasi phase matching.

We report the demonstration of spatially translating a stored optical pulse at room temperature over distances exceeding one optical wavelength. By implementing an interferometric scheme, we further measure the average speed of this linear translation, thus harnessing a stopped-light experiment for a sensing application. This work extends the use of quantum memories beyond quantum communication and information contexts, opening a pathway to novel methods of velocity measurements with high sensitivity.

We demonstrate that a nonmagnetic silicon nanoparticle dimer can scatter visible light as a pure magnetic scatterer under plane-wave illumination, with magnetic resonance dominant and electric dipole responses suppressed. This is achieved by spectrally overlapping the magnetic dipole resonance with the electric toroidal and magnetic quadrupole modes. Then the destructive interference between the Cartesian electric dipole and the electric toroidal mode suppresses the spherical electric dipole response and thus generates a nonradiating anapole mode, enabling ideal magnetic resonance scattering with overlapping magnetic dipole and quadrupole responses in the far field. Moreover, the wavelengths of magnetic resonance responses are tunable in the visible light range.

We consider the quantum simulation of quadratic spin-phonon coupling in a crystal of trapped ions. The coupling is implemented using tightly focused optical tweezers on each ion that change the local trapping potential in a state-dependent way. By encoding spins in the internal states of the ions and adding a tunneling term via Mølmer-Sørensen-type interactions, we calculate the emergence of mobile bipolarons driven by the zero-point energy of the ion crystal phonons. We show that thermal occupation may pin the bipolarons for ion crystals at finite temperature. Our scheme can be used to study and illustrate the emergence of mobile bipolarons as a function of temperature.

The large majority of topological phases in one-dimensional many-body systems are known to be inherited from the corresponding single-particle Hamiltonian. In this work, we go beyond this assumption and find a new example of topological order induced through specific interaction couplings. Specifically, we consider a fermionic mixture where one component experiences a staggered on-site potential and it is coupled through density-dependent hopping interactions to the other fermionic component. Crucially, by varying the sign of the staggered potential, we show that this latter fermionic component can acquire topological properties. Due to matrix product state simulations, we prove this result both at equilibrium by extracting the behavior of correlation functions and in an out-of-equilibrium scheme by employing a Thouless charge pumping. Notably, we further discuss how our results can be probed in quantum simulators made up of ultracold atoms. Our results reveal an important and alternative mechanism that can give rise to topological order.

High-order harmonic generation (HHG) of an atom in a strong laser field provides a broad spectral bandwidth for attosecond pulse synthesis. However, due to complex electron dynamics in the atom, usually only a part of the HHG can be used for the synthesis of the attosecond pulse, which significantly limits the attosecond pulse width. In this work we theoretically study the synthesis of attosecond pulses from high-order harmonics generated by intense squeezed light. It is found that, unlike the coherent light, the whole HHG spectrum can be effectively used to synthesize attosecond pulses. By developing strong-field approximation theory in squeezed light, this is attributed to substantial suppression of long and multireturn electron trajectories at the single-atom level. Based on this novel scheme using intense squeezed light, we show that an isolated attosecond pulse can be synthesized from the entire HHG spectrum, and the pulse width is much shorter than that from the coherent light with the same laser parameters.

We investigate the possibility of using a Rabi drive to tune the interactions in an atomic Fermi gas. Specifically, we consider the scenario where two fermion species (spins) are Rabi coupled and interacting with a third uncoupled species. Using an exact calculation within a minimal low-energy model, we derive analytical expressions for the effective scattering length and effective range that characterize the collisions between a Rabi-dressed atom and an atom from the third species. In particular, we find that new scattering resonances emerge in the Rabi-coupled system, which we demonstrate are linked to the existence of hybrid two-body bound states. Furthermore, we show via a generalized Thouless criterion that the scattering properties have a direct impact on the superfluid transitions in the Rabi-coupled Fermi gas. The presence of Rabi-induced resonances thus has implications for the investigation of many-body physics with driven atomic gases.

A surprising result from the theory of quantum control is the degree to which the properties of a physical system can be manipulated. Both atomic and many-body solid-state models admit the possibility of creating a “driven imposter” in which the optical response of one material mimics that of a dynamically distinct system. Here we apply these techniques to polarons in polar liquids. Such quasiparticles describe solvated electrons interacting with many-body degrees of freedom of their environment. The polaron frequency, which depends on the electron concentration in the liquid, is controlled with a pump field. Using this field as a control, we demonstrate the aforementioned dynamical mimicry experimentally, rendering the polaron frequency of three different liquids identical.

The scaling of local quantum entropies is of utmost interest for characterizing quantum fields, many-body systems, and gravity. Despite their importance, theoretically and experimentally accessing quantum entropies is challenging as they are nonlinear functionals of the underlying quantum state. Here, we show that suitably chosen classical entropies capture many features of their quantum analogs for an experimentally relevant setting. We describe the postquench dynamics of a multiwell spin-1 Bose-Einstein condensate from an initial product state via measurement distributions of spin observables and estimate the corresponding entropies using the asymptotically unbiased $k$-nearest-neighbor method. We observe the dynamical buildup of quantum correlations signaled by an area law, as well as local thermalization revealed by a transition to a volume law, both in regimes characterized by non-Gaussian distributions. We emphasize that all relevant features can be observed at small sample numbers without reconstructing the underlying state or measurement distributions, rendering our method directly applicable to a large variety of models and experimental platforms.

Methods to generate photons with tailored indistinguishability are central to developing photonic quantum technologies and making fundamental tests of quantum physics. This study introduces a novel method for manipulating effective longitudinal spatial coherence (LSC) of biphotons, controlling their indistinguishability in a significant manner. The experimental results show that, instead of tailoring the frequency spectrum of the interfering photons, changing their LSC also leads to controlling the width of Hong-Ou-Mandel dip as validated by the theoretical calculations. This powerful approach not only modifies the conventional wisdom claiming only frequency width responsible for indistinguishability control of photons but also positions the LSC as a promising tool for fine-tuning the longitudinal coherence of photons, thereby expanding their potential use in quantum science and technologies.

The energy cost of erasing a bit of information was fundamentally lower bounded by Landauer, in terms of the temperature of its environment, $W\ge k_{\mathrm{B}}Tln2$. Energy consumption and heat generation in computers is now a pressing issue, but real electronic devices operate out of equilibrium and are subject to other noise sources besides temperature. Considering a quantum dot charge bit as a concrete model, we here derive a tighter bound, rigorously quantifying the dissipative impact of lifetime broadening and potential difference, in terms of a few experimentally measurable parameters. In practical contexts, these additional contributions may significantly outweigh the cost due to temperature alone. The results shed light not only on theoretical limits of erasure but also on constraints in realistic devices.

We propose a procedure to engineer solid-state lattice models with superlattices of interaction-coupled Bose-Einstein condensates. We show that the dynamical equation for the excitations of Bose-Einstein condensates at zero temperature can be expressed in an eigenvalue form that resembles the time-independent Schrödinger equation. The eigenvalues and eigenvectors of this equation correspond to the dispersions of the collective modes and the amplitudes of the density oscillations. This likeness opens the way for the simulation of different tight-binding models with arrays of condensates. We demonstrate, in particular, how we can model a one-dimensional Su-Schrieffer-Heeger lattice supporting topological edge modes and a two-dimensional Lieb lattice with flat-band excitations with superlattices of Bose-Einstein condensates.

For an efficient usage and deployment of entanglement, we envisage the scenario where a pair of spatially separated observers, Charu and Debu, want to share entanglement without interacting with each other. As a way out, their systems can separately and locally interact with those of Alice and Bob, respectively, who already share an entangled state. We find joint unitaries which, when applied by Alice and a Charu, and by Bob and the corresponding Debu, can transfer entanglement from the Alice-Bob pair to an indefinite number of pairs of Charus and Debus. We also discuss the amount of entanglement that can be transferred to a fixed number of pairs using these unitaries. Moreover, by optimizing over all possible local unitaries, we analyze the maximum number of pairs to which entanglement can be transferred in such a way that each pair gets at least a fixed amount of entanglement. Given the valuable role played by the costly resource, entanglement, in quantum information processing and communication, we expect that our results will have significant impact in quantum technologies.

Accurately describing nuclear interactions within atomic nuclei remains a challenge, which hinders our exploration of new physics beyond the Standard Model. However, these nuclear interactions can be characterized by nuclear parameters such as the Zemach radius and the electric quadrupole moment, which are reflected in atomic spectra. Our work achieves high-precision measurements of lithium-ion hyperfine splittings at the level of 10 kHz, and directly extracts these important nuclear structure parameters. We observe significant discrepancies between our results and both nuclear theory and molecular spectra regarding the electric quadrupole moment. The result for ${}^7\mathrm{Li}$ deviates by $2.3\sigma$ from the currently recommended value, whereas the result for ${}^6\mathrm{Li}$ deviates by up to $6.2\sigma$ from the recommended value determined by molecular spectroscopy. We supplement the measurements with independent calculations based on nuclear structure theory. They provide support for the results obtained from the present ion spectroscopy measurements. Our results provide valuable information for characterizing nuclear forces, serve as sensitive benchmarks for testing nuclear structure theories, and enable critical comparisons with both electron-nuclear scattering and molecular spectroscopy.

We report on the realization and characterization of a novel magic-wavelength nanofiber-based two-color optical dipole trap for cesium that allows us to generate two diametral periodic one-dimensional arrays of trapping sites with a spacing significantly smaller than half the resonant free-space wavelength of the cesium $D_2$ transition. This is achieved by launching a blue-detuned partial standing wave and two red-detuned light fields through the nanofiber. We trap and optically interface the atoms in the resulting periodic optical potential and characterize the trap by measuring the lifetime of the trapped atoms, the atom-light coupling strength, the filling factor, and the trap frequencies in the radial and axial directions. The implementation of this nanofiber-based optical interface with magic trapping wavelengths and sub-$\lambda /2$ spacing is an important step towards the exploration of novel collective radiative effects, such as selective radiance.

A quantum algorithm for simulating multidimensional scalar transport problems using a time-marching strategy is presented. A direct unitary block encoding of the explicit time-marching operator is constructed, resulting in the intrinsic success probability of the squared solution norm without the need for amplitude amplification, thereby retaining a linear dependence on the simulation time. The algorithm separates the explicit time-marching operator into an advection-like component and a corrective shift operator. The advection-like component is mapped to a Hamiltonian simulation and combined with the shift operator through the linear combination of unitaries algorithm. State-vector simulations of a scalar transported in a steady two-dimensional Taylor-Green vortex support the theoretical findings.

Ultracold dipolar hard-core bosons in optical ladders provide exciting possibilities for the quantum simulation of anisotropic spin ladders. We show that introducing a tilt along the rungs results in a rich phase diagram at unit rung filling. In particular, for a sufficiently strong dipolar strength, the interplay between the long-range tail of the dipolar interactions and the tilting leads to the emergence of a quantum floating phase, a critical phase with incommensurate density-density correlations. Interestingly, the floating phase is topological, constituting an intermediate gapless stage in the melting of a crystal into a gapped topological Haldane phase. This novel scenario for topological floating phases in dipolar spin ladders can be investigated in ongoing experiments.

Twisted photons carrying orbital angular momentum, which have potential applications spanning diverse fields, have been extensively studied since the theoretical work of Allen et al. in 1992. Various methods for direct producing twisted photons have been explored, leveraging the rotational (spiral) motion of relativistic electrons in phenomena such as undulator radiation. In the present study, transition radiation carrying orbital angular momentum is observed. This radiation was generated by 220 MeV electrons incident on an Au-coated Si wafer. The orbital angular momentum was measured by analyzing the diffraction patterns produced as the radiation passed through a triangular aperture and a double slit. These results demonstrate that twisted photons can also be generated through the interaction of rectilinearly moving electrons with a solid target.

Quantum error correction suppresses noise in quantum systems to allow for high-precision computations. In this Letter, we introduce multivariate bicycle quantum low-density parity-check (QLDPC) codes, via an extension of the framework developed by Bravyi et al. [S. Bravyi, A. W. Cross, J. M. Gambetta, D. Maslov, P. Rall, and T. J. Yoder, Nature (London) 627, 778 (2024)], and particularly focus on trivariate bicycle (TB) codes. Unlike the weight-6 codes proposed in their study, we offer concrete examples of weight-5 TB-QLDPC codes which promise to be more amenable to near-term experimental setups. We show that TB-QLDPC codes up to weight 6 have a biplanar structure and often possess a two-dimensional toric layout. Under circuit level noise, we find substantially better encoding rates than comparable surface codes while offering similar error suppression capabilities. For example, we can encode four logical qubits with distance 5 into 60 physical qubits using weight-5 check measurements of circuit depth 7, while a surface code with these parameters requires 200 physical qubits. The high encoding rate and compact layout make our codes highly suitable candidates for near-term hardware implementations, paving the way for a realizable quantum error correction protocol.