The growing number of patients who require organ transplants, combined with the low number of organ donors, has resulted in organ shortages; therefore, the fabrication of human tissues and organs is an urgent need. However, the time required to fabricate an organ may result in risky delays for end-stage patients who urgently require transplants. During bioprinting, the maturation of the engineered tissue that is required before it is ready for implantation is lengthy. Here we use a previously introduced microscopic and mathematical model, the “zipper CAMs” (for ell dhesion olecules), to investigate the effective parameters involved in tissue dynamics. In our current study, we validated the ability of our model to accelerate the tissue maturation process. Our model shows that exploiting cellular mechanotransduction can accelerate post-printing tissue maturation. To verify this prediction experimentally, we devised a mechanotransduction-based bioprinter that accelerates the production of tissues by speeding up the fusion bioink particles. The mathematical microscopic model and the bioprinter described herein are expected to be highly useful in cell biology, tissue engineering, and biofabrication.

Strongly coupled quantum fields, such as multicomponent atomic condensates, optical fields, and polaritons, are remarkable systems where the simple dynamics of coupled oscillators can meet the intricate phenomenology of quantum fluids. When the coupling between the components is coherent, not only the particles' number, but also their phase texture that maps the linear and angular momentum, can be exchanged. Here, on a system of exciton polaritons, we have realized a so-called full-Bloch beam: a configuration in which all superpositions of the upper and the lower polaritons—all quantum states of the associated Hilbert space—are simultaneously present at different points of the physical space, evolving in time according to Rabi-oscillatory dynamics. As a result, the light emitted by the cavity displays a peculiar dynamics of spiraling vortices endowed with oscillating linear and angular momenta and exhibiting ultrafast motion of their cores with striking accelerations to arbitrary speeds. This remarkable vortex motion is shown to result from distortions of the trajectories by a homeomorphic mapping between the Rabi rotation of the full wave function on the Bloch sphere and Apollonian circles in the real space where the observation is made. Such full-Bloch beams offer prospects at a fundamental level regarding their topological properties or in the interpretation of quantum mechanics, and the Rabi-rotating vortices they yield should lead to interesting applications such as ultrafast optical tweezers.

Curie's principle states that “when effects show certain asymmetry, this asymmetry must be found in the causes that gave rise to them.” We demonstrate that symmetry equivariant neural networks uphold Curie's principle and can be used to articulate many symmetry-relevant scientific questions as simple optimization problems. We prove these properties mathematically and demonstrate them numerically by training a Euclidean symmetry equivariant neural network to learn symmetry breaking input to deform a square into a rectangle and to generate octahedra tilting patterns in perovskites.

A projective symmetry group (PSG) has been regarded as a classification theory of spin liquids. However, it does not include a symmetry-protected topological order of fermionic spinon excitations, and thus the classification of gapped spin liquids is incomplete. We demonstrate the classification beyond PSG by utilizing the Kitaev model on the square-octagon lattice, where two gapped spin liquids are distinguished by a topological $Z_2$ invariant. This $Z_2$ invariant can be defined solely by the time-reversal and translation symmetries on condition that the time-reversal symmetry is implemented projectively. Thus, it is a hidden class of topological Kitaev spin liquids with helical edge states, which has been ignored for a long time. This suggests that there exists an unknown classification scheme of gapped spin liquids beyond PSG.

A quantum receiver is an essential element of quantum illumination (QI), which outperforms its classical counterpart, called classical illumination. However, there are only few proposals for realizable quantum receiver, which exploits nonlinear effects leading to increasing the complexity of receiver setups. To compensate this, in this paper, we design a quantum receiver with linear optical elements for Gaussian QI. Rather than exploiting nonlinear effect, our receiver consists of a 50:50 beam splitter and homodyne detection. Using double homodyne detection after the 50:50 beam splitter, we analyze the performance of the QI in different regimes of target reflectivity, source power, and noise level. We show that our receiver has better signal-to-noise ratio and is more robust against noise than the existing simple-structured receivers.

The paper reports on the optical detection and spectroscopy of ultracold atoms near a gold surface. A probe light field is used to excite surface plasmon polaritons. The refractive index of the atomic gas shifts the plasmon resonance and changes the reflected light power. Thus, the sensitivity of the detection is plasmonically enhanced. Absorption of photons from the evanescent wave is avoided by detuning the laser from atomic resonance which makes the detection scheme potentially nondestructive. The spectrum of the signal is determined by a Fano resonance. We show that atoms can be detected nondestructively with single atom resolution for typical parameters in cold atom experiments. Thus, the method is suitable for quantum nondemolition measurements of matter wave amplitudes. Experimentally, we measure a technically limited sensitivity of 30 atoms and extend the detection scheme to dispersively image the atom cloud near the surface.

Motivated by recent progress of quantum technologies making small-scale programmable quantum computing possible, here we study a discretized quantum adiabatic process for a one-dimensional free-fermion system described by a variational wave function, i.e., a parametrized quantum circuit. The wave function is composed of $M$ layers of two elementary sets of time-evolution operators, each set being decomposed into commutable local operators acting on neighboring sites. The evolution time of each time-evolution operator is treated as a variational parameter so as to minimize the expectation value of the energy. We show that the exact ground state is reached by applying the layers of time-evolution operators as many as a quarter of the system size, implying that at least in this case, the state is exactly prepared in a quantum circuit with linear depth. This is the minimum number $M_B$ of layers set by the limit of speed, i.e., the Lieb-Robinson bound, for propagating quantum entanglement via the local time-evolution operators. Indeed, we show the mutual information of the variational wave function that reveals a causality-cone-like structure in the propagation of quantum entanglement. Quantities such as the energy $E$ and the entanglement entropy $S$ of the optimized variational wave function with the number $M$ of layers less than $M_B$ are independent of the system size $L$ but fall into some universal functions of $M$, indicating that the entanglement generated in this variational ansatz with a finite $M$ is bounded, as in the case of the matrix product states with a finite bond dimension. Furthermore, in this case, we find that these two quantities behave asymptotically as $E/L-{\varepsilon }_{\infty }\sim M^{-2}$ (${\varepsilon }_{\infty }$: the exact ground-state energy per site in the thermodynamic limit) and $S\approx \frac{1}{3}lnM$. The development of the entanglement in the variational ansatz through the discretized quantum adiabatic process is further manifested in the progressive propagation of single-particle orbitals in the variational wave function. We also find that the optimized variational parameters converge systematically to a smooth function of the discretized time, which provides the optimum scheduling function in the quantum adiabatic process, with the effective total evolution time of the variational ansatz to the exact ground state being proportional to the system size $L$. This is a drastic improvement compared to the evolution time proportional to $L^2$ for the continuous-time quantum adiabatic process with a linear scheduling and is attributed to diabaticity of the discretized quantum adiabatic process represented in the variational ansatz. Finally, we investigate the imaginary-time evolution counterpart of this variational wave function, where the causality relation is absent due to the nonunitarity of the imaginary-time evolution operators, and thus the norm of the wave function is no longer conserved. We find that the convergence to the exact ground state is exponentially fast, despite that the system is at the critical point, suggesting that implementation of the nonunitary imaginary-time evolution in a quantum circuit is highly promising to further shallow the circuit depth, provided that the local nonunitary operators are represented with a reasonable amount of unitary operators.

We study the spin transport through a 1D quantum Ising-XY-Ising spin link that emulates a topological superconducting-normal-superconducting structure via Jordan-Wigner (JW) transformation. We calculate, both analytically and numerically, the spectrum of spin Andreev bound states and the resulting ${\mathbb{Z}}_2$ fractional spin Josephson effect (JE) pertaining to the emerging Majorana JW fermions. Deep in the topological regime, we identify an effective time-reversal symmetry that leads to ${\mathbb{Z}}_4$ fractional spin JE in the presence of interactions within the junction. Moreover, we uncover a hidden inversion time-reversal symmetry that protects the ${\mathbb{Z}}_4$ periodicity in chains with an odd number of spins, even in the absence of interactions. We also analyze the entanglement between pairs of spins by evaluating the concurrence in the presence of spin current and highlight the effects of the JW Majorana states. We propose to use a microwave cavity setup for detecting the aforementioned JEs by dispersive readout methods and show that, surprisingly, the ${\mathbb{Z}}_2$ periodicity is immune to any local magnetic perturbations. Our results are relevant for a plethora of spin systems, such as trapped ions, photonic lattices, electron spins in quantum dots, or magnetic impurities on surfaces.

We explore the formation and collective modes of Bose-Einstein condensate of Dirac magnons (Dirac BEC). While we focus on two-dimensional Dirac magnons, an employed approach is general and could be used to describe Bose-Einstein condensates with linear quasiparticle spectrum in various systems. By using a phenomenological multicomponent model of pumped boson population together with bosons residing at Dirac nodes, the formation and time evolution of condensates of Dirac bosons is investigated. The condensate coherence and its multicomponent nature are manifested in the Rabi oscillations whose period is determined by the gap in the spin-wave spectrum. A Dirac nature of the condensates could be also probed by the spectrum of collective modes. It is shown that the Haldane gap provides an efficient means to tune between the gapped and gapless collective modes as well as controls their stability.

Hund's coupling in multiorbital systems allows for the possibility of even-parity orbital-antisymmetric spin-triplet pairing, which can be stabilized by spin-orbit coupling (SOC). While this pairing expressed in the orbital basis is uniform and spin-triplet, it appears in the band basis as a pseudospin-singlet, with the momentum dependence determined by the SOC and the underlying triplet character remaining in the form of interband pairing active away from the Fermi energy. Here, we examine the role of momentum-dependent SOC in generating nontrivial pairing symmetries, as well as the hidden triplet nature associated with this interorbital pairing, which we dub a “shadowed triplet.” Applying this concept to ${\mathrm{Sr}}_2{\mathrm{RuO}}_4$, we first derive several forms of SOC with $d$-wave form factors from a microscopic model, and subsequently we show that for a range of SOC parameters, a pairing state with $s+i{d}_{xy}$ symmetry can be stabilized. Such a pairing state is distinct from pure spin-singlet and -triplet pairings due to its unique character of pseudospin-energy locking. We discuss experimental probes to differentiate the shadowed triplet pairing from conventional pseudospin-triplet and -singlet pairings.

Atomic spectral lines for different isotopes are shifted, revealing a change in the properties of the nucleus. For spinless nuclei such isotope shifts for two distinct transitions are expected to be linearly related, at least at leading order in a change of the nuclear mass and charge distribution. Looking for a breaking of linearity in so-called King plots was proposed as a novel method to search for physics beyond the standard model. In the light of the recent experimental progress in isotope shift spectroscopy, the sensitivity of these searches will become limited by the determination of the isotope masses and/or by nuclear effects which may induce nonlinearities at an observable level. In this work, we propose two possible generalizations of the traditional King plot that overcome these limitations by including additional isotope shift measurements, thus significantly extending the new physics reach of King plots in a purely spectroscopy-driven approach.

A number of tools have been developed to detect topological phase transitions in strongly correlated quantum systems. They apply under different conditions, but do not cover the full range of many-body models. It is hence desirable to further expand the toolbox. Here, we propose to use quasiparticle properties to detect quantum phase transitions. The approach is independent from the choice of boundary conditions, and it does not assume a particular lattice structure. The probe is hence suitable for, e.g., fractals and quasicrystals. The method requires that one can reliably create quasiparticles in the considered systems. In the simplest cases, this can be done by a pinning potential, while it is less straightforward in more complicated systems. We apply the method to several rather different examples, including one that cannot be handled by the commonly used probes, and in all the cases we find that the numerical costs are low. This is so, because a simple property, such as the charge of the anyons, is sufficient to detect the phase transition point. For some of the examples, this allows us to study larger systems and/or further parameter values compared to previous studies.

The self-learning metropolis-Hastings algorithm is a powerful Monte Carlo method that, with the help of machine learning, adaptively generates an easy-to-sample probability distribution for approximating a given hard-to-sample distribution. This paper provides a new self-learning Monte Carlo method that utilizes a quantum computer to output a proposal distribution. In particular, we show a novel subclass of this general scheme based on the quantum Fourier transform circuit; when the dimension of the input to QFT corresponding to the low-frequency components is not large, this sampler is classically simulable while having a certain advantage over conventional methods. The performance of this quantum-inspired algorithm is demonstrated by some numerical simulations.

The potential energy landscape (PEL) formalism is a theoretical approach within statistical mechanics used extensively in the past to study classical liquids and glasses. Here, we extend the PEL formalism to the case of quantum liquids. As an example, we apply the PEL approach to study a family of quantum monatomic liquids using path-integral Monte Carlo simulations. We focus on the energy $\left(E_{\text{IS}}\right)$ and pressure $\left(P_{\text{IS}}\right)$ of the local minima of the PEL [inherent structures (IS)] explored by the liquids. It is found that, similar to the classical case, the quantum liquids exhibit a PEL-independent regime at high temperatures and a PEL-influenced regime at low temperatures, where the topography of the PEL plays a major role. Interestingly, the PEL of all the quantum liquids studied is Gaussian, providing a simple expression for the configurational entropy of the liquids. Remarkably, the ring-polymers representing the atoms of the quantum liquids are collapsed at the IS. Accordingly, an IS of the quantum liquid, in its own PEL, is also an IS of the classical liquid in the classical liquid PEL (CL-PEL). A pictorial interpretation of the behavior of quantum liquids using the CL-PEL (as opposite to the quantum liquid PEL) is provided. In this view, the quantum liquid is represented by a pancakelike patch that expands over multiple IS of the CL-PEL, changing shape with time while describing a fuzzy trajectory (on the CL-PEL). The formalism described in this work is general and can, in principle, be extended to quantum systems other than liquids.

Experimentally there exist many materials with first-order phase transitions at finite temperature that display quantum criticality. Classically, a strain-energy density coupling is known to drive first-order transitions in compressible systems, and here we generalize this Larkin et al. [Zh. Eksp. Teor. Fiz. 56, 1664 (1969) [Sov. Phys. JETP 29, 891 (1969)]] mechanism to the quantum case. We show that if the $T=0$ system lies above its upper critical dimension, the line of first-order transitions ends in a “quantum annealed critical point” where zero-point fluctuations restore the underlying criticality of the order parameter. The generalized Larkin-Pikin phase diagram is presented and experimental consequences are discussed.

This paper presents an exact analytical theory for field emission from dielectric coated cathode surfaces, by solving the one-dimensional (1D) Schrödinger equation with a double-triangular potential barrier introduced by the coating. The effects of the cathode material (work function and Fermi energy), dielectric properties (dielectric constant, electron affinity, and thickness), applied dc field strength, and cathode temperature are analyzed in detail. For 1D flat cathode surfaces with coating, it is found that the emission current density can be larger than the uncoated case when the dielectric constant is smaller than a certain value ${\varepsilon }_{\mathrm{diel}}^{\mathrm{th}}$ and the dielectric thickness is larger than the threshold value $d_{\mathrm{th}}\left[\mathrm{nm}\right]\approx {\varepsilon }_{\mathrm{diel}}W/eF$ with the dielectric constant ${\varepsilon }_{\mathrm{diel}}<{\varepsilon }_{\mathrm{diel}}^{\mathrm{th}}$, where $W$ is the work function of the cathode material, $F$ the applied dc field, and $e$ the elementary charge. Our quantum model is also compared with a modified Fowler-Nordheim equation for a double barrier, showing qualitatively good agreement. Our study provides insights for designing field emitters with higher efficiency and better stability.

We initiate quantitative studies of complexity in (1+1)-dimensional conformal field theories with a view that they provide the simplest setting to find a gravity dual to complexity. Our work pursues a geometric understanding of the complexity of conformal transformations and embeds Fubini-Study state complexity and direct counting of stress tensor insertion in the relevant circuits in a unified mathematical language. In the former case, we iteratively solve the emerging integrodifferential equation for sample optimal circuits and discuss the sectional curvature of the underlying geometry. In the latter case, we recognize that optimal circuits are governed by Euler-Arnold type equations and discuss relevant results for three well-known equations of this type in the context of complexity.

The fractionalization of microscopic degrees of freedom is a remarkable manifestation of strong interactions in quantum many-body systems. Analytical studies of this phenomenon are primarily based on two distinct frameworks: field theories of partons and emergent gauge fields, or coupled arrays of one-dimensional quantum wires. We unify these approaches for two-dimensional spin systems. Via exact manipulations, we demonstrate how parton gauge theories arise in microscopic wire arrays and explicitly relate spin operators to emergent quasiparticles and gauge-field monopoles. This correspondence allows us to compute physical correlation functions within both formulations and leads to a straightforward algorithm for constructing parent Hamiltonians for a wide range of exotic phases. We exemplify this technique for several chiral and nonchiral quantum spin liquids.

In spite of the (correct) common-wisdom statement correlation does not imply causation, a proper employ of time correlations and of fluctuation-response theory allows us to understand the causal relations between the variables of a multidimensional linear Markov process. It is shown that the fluctuation-response formalism can be used both to find the direct causal links between the variables of a system and to introduce a degree of causation, cumulative in time, whose physical interpretation is straightforward. Although for generic nonlinear dynamics there is no simple exact relationship between correlations and response functions, the described protocol can still give a useful proxy also in the presence of weak nonlinear terms.

Yttrium sulfides are found to exhibit rich phase diagram and diverse properties under pressures. Here, we systematically investigate the stability of binary Y-S system up to 50 GPa using first-principles swarm-intelligence structure search. We identify seven hitherto unknown stoichiometries (${\mathrm{Y}}_7{\mathrm{S}}_6$, ${\mathrm{Y}}_6{\mathrm{S}}_5$, ${\mathrm{Y}}_7{\mathrm{S}}_8$, ${\mathrm{Y}}_6{\mathrm{S}}_7$, ${\mathrm{Y}}_5{\mathrm{S}}_6$, ${\mathrm{Y}}_3{\mathrm{S}}_2$, and ${\mathrm{YS}}_3$) that are energetically stable with respect to the decomposition into elemental components. All phases exhibit metallic nature, of which ${\mathrm{YS}}_3$ shows potential superconductivity with estimated $T_c$ of 18.5 K at 50 GPa. The $T_c$ in ${\mathrm{YS}}_3$ is comparable to the 17 K superconductivity in elements yttrium (89.3 GPa) and sulfur (160 GPa), but could be achieved at much lower pressure. The high superconductivity is attributed to the high electronic density of states from S atoms at Fermi level. Additionally, ${\mathrm{Y}}_3{\mathrm{S}}_2$ is predicted to be a layer-structured magnetic electride with magnetic moment of 0.5 $\mu B$ per formula unit at 6 GPa, which transforms to a three-dimensional phase with weak superconductivity around 17 GPa.