We generate and characterise entangled states of a register 20 individually controlled qubits, where each qubit is encoded into the electronic state trapped atomic ion. Entanglement generated amongst qubits during out-of-equilibrium dynamics an Ising-type Hamiltonian, engineered via laser fields. Since qubit-qubit interactions decay with distance, entanglement at early times predominantly between neighbouring groups qubits. these by designing applying witnesses for genuine multipartite...

A novel framework identifies the necessary thermodynamic resources for producing pure quantum states, connecting third law of thermodynamics with Landauer's principle and highlighting role information complexity in thermodynamics.

We analyze fermionic modes as fundamental entities for quantum information processing. To this end we construct a density operator formalism on the underlying Fock space and demonstrate how it can be naturally unambiguously equipped with notion of subsystems in absence global tensor product structure. argue that any apparent similarities between qubits are superficial only applied limited situations. In particular, discuss ambiguities arise from different treatments subject. Our results...

Quantum error correction is widely thought to be the key fault-tolerant quantum computation. However, determining most suited encoding for unknown channels or specific laboratory setups highly challenging. Here, we present a reinforcement learning framework optimizing and fault-tolerantly adapting codes. We consider agent tasked with modifying family of surface code memories until desired logical rate reached. Using efficient simulations about 70 data qubits arbitrary connectivity,...

We show that it is impossible to perform ideal projective measurements on quantum systems using finite resources. identify three fundamental features of and when limited by resources only one these can be salvaged. Our framework general enough accommodate any system measuring device (pointer) models, but for illustration we use an explicit model <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>N</mml:mi></mml:math>-particle pointer. For a pointer perfectly reproduces the...

One of the most fundamental tasks in quantum thermodynamics is extracting energy from one system and subsequently storing this an appropriate battery. Both these steps, work extraction charging, can be viewed as cyclic Hamiltonian processes acting on individual systems. Interestingly, so-called passive states exist, whose cannot lowered by unitary operations, but it safe to assume that any not fully charged battery may increased unitarily. However, unitaries raising average same amount...

We study the effects of relativistic motion on quantum teleportation and propose a realizable experiment where our results can be tested. compute bounds optimal fidelity when one observers undergoes nonuniform for finite time. The upper bound to is degraded due observer's motion. However, we discuss how this degradation corrected. These are observable experimental parameters that within reach cutting-edge superconducting technology.

Entanglement shared among multiple parties presents complex challenges for the characterisation of different types entanglement. One most fundamental insights is fact that some mixed states can feature entanglement across every possible cut a multipartite system yet be produced via mixture separable with respect to partitions. To distinguish genuinely cannot from mixing such partition-separable states, term genuine was coined. All these considerations originate in paradigm where only single...

We describe the spin and momentum degrees of freedom a system two massive spin-$\frac{1}{2}$ particles as four-qubit system. Then we explicitly show how entanglement changes between different partitions qubits, when considered by inertial observers. Although particle corresponding to partition into Alice's Bob's subsystems is, often stated in literature, invariant under Lorentz boosts, with respect other Hilbert space on hand, is not. It certainly does depend chosen frame initial state...

We present setups for the practical realization of adding control to unknown subroutines, supplementing existing quantum optical scheme black-box with a counterpart ordering sequences operations. also provide schemes realize either task using trapped ions. These circumventions recent no-go theorems are based on technologies. argue that possibility add operations in practice is common feature many physical systems. Based proposed implementations we discuss apparent contradictions between...

We analyze quantized scalar, spinor, and photon fields in a mechanically rigid cavity that is accelerated Minkowski spacetime, recently introduced perturbative small-acceleration formalism allows the velocities to become relativistic, with view applications relativistic quantum information. A scalar field analyzed both Dirichlet Neumann boundary conditions, under perfect conductor conditions shown decompose into Dirichlet-like Neumann-like polarization modes. The Dirac spinor nonvanishing...

Abstract Coherent controlization, i.e., coherent conditioning of arbitrary single- or multi-qubit operations on the state one more control qubits, is an important ingredient for flexible implementation many algorithms in quantum computation. This particular significance when certain subroutines are changing over time they frequently modified, such as decision-making learning agents. We propose a scheme to realize controlization any number superconducting qubits coupled microwave resonator....

We address the issue of precisely estimating small parameters encoded in a general linear transformation modes bosonic quantum field. Such Bogoliubov transformations frequently appear context optics. provide set instructions for computing Fisher information arbitrary pure initial states. show that maximally achievable precision estimation is inversely proportional to squared average particle number and such Heisenberg scaling requires nonclassical but not necessarily entangled Our method...

Quantum metrology offers a quadratic advantage over classical approaches to parameter estimation problems by utilising entanglement and nonclassicality. However, the hurdle of actually implementing necessary quantum probe states measurements, which vary drastically for different metrological scenarios, is usually not taken into account. We show that wide range tasks in metrology, 2D cluster (a particular family useful measurement-based computation) can serve as flexible resources allow one...

Photons offer the potential to carry large amounts of information in their spectral, spatial, and polarisation degrees freedom. While state-of-the-art classical communication systems routinely aim maximize this information-carrying capacity via wavelength spatial-mode division multiplexing, quantum based on multi-mode entanglement usually suffer from low state quality, long measurement times, limited encoding capacity. At same time, certification methods often rely assumptions that...

Within quantum thermodynamics, many tasks are modeled by processes that require work sources represented out-of-equilibrium systems, often dubbed batteries, in which can be deposited or from extracted. Here we consider batteries as finite-dimensional systems initially thermal equilibrium charged via cyclic Hamiltonian processes. We present optimal near-optimal protocols for <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mi>N</a:mi></a:math> identical two-level and individual <b:math...

Landauer's limit on heat dissipation during information erasure is critical as devices shrink, requiring optimal pure-state preparation to minimize errors. However, Nernst's third law states this demands infinite resources in energy, time, or control complexity. We address the challenge of cooling quantum systems with finite resources. Using Markovian collision models, we explore resource trade-offs and present efficient protocols (that are for qubits) coherent incoherent control. Leveraging...

Abstract Certifying entanglement is an important step in the development of many quantum technologies, especially for higher-dimensional systems, where promises increased capabilities communication and computation. A key feature distinguishing from classical correlations occurrence complementary measurement bases. In particular, mutually unbiased bases (MUBs) are a paradigmatic example that well-understood routinely employed certification. However, implementing measurements exactly...

We present a general, analytic recipe to compute the entanglement that is generated between arbitrary, discrete modes of bosonic quantum fields by Bogoliubov transformations. Our setup allows complete characterization correlations in all Gaussian field states. Additionally, it holds for These are commonly applied optics description squeezing operations, relate mode decompositions observers different regions curved spacetimes, and describe moving along non-stationary trajectories. focus on...

We establish a rigorous connection between fundamental resource theories at the quantum scale. Correlations and entanglement constitute indispensable resources for numerous information tasks. However, their establishment comes cost of energy, thermodynamics, is limited by initial entropy. Here, optimal conversion energy into correlations investigated. Assuming presence thermal bath, we general bounds arbitrary systems construct protocol saturating them. The amount correlations, quantified...

We show that any quantum information theory based on anticommuting operators must be supplemented by a superselection rule deeply rooted in relativity to establish reasonable notion of entanglement. While may encoded the fermionic Fock space, unrestricted has peculiar feature: The marginals bipartite pure states need not have identical entropies, which leads an ambiguous definition solve this problem, proving it is removed relativity, i.e., parity arises from Lorentz invariance via...