Measurement-induced entanglement and teleportation on a noisy quantum processor

Measurement has a special role in quantum theory: by collapsing the wavefunction it can enable phenomena such as teleportation and thereby alter the "arrow of time" that constrains unitary evolution. When integrated in many-body dynamics, measurements can lead to emergent patterns of quantum information in space-time that go beyond established paradigms for characterizing phases, either in or out of equilibrium. On present-day NISQ processors, the experimental realization of this physics is challenging due to noise, hardware limitations, and the stochastic nature of quantum measurement. Here we address each of these experimental challenges and investigate measurement-induced quantum information phases on up to 70 superconducting qubits. By leveraging the interchangeability of space and time, we use a duality mapping, to avoid mid-circuit measurement and access different manifestations of the underlying phases -- from entanglement scaling to measurement-induced teleportation -- in a unified way. We obtain finite-size signatures of a phase transition with a decoding protocol that correlates the experimental measurement record with classical simulation data. The phases display sharply different sensitivity to noise, which we exploit to turn an inherent hardware limitation into a useful diagnostic. Our work demonstrates an approach to realize measurement-induced physics at scales that are at the limits of current NISQ processors

Non-Abelian braiding of graph vertices in a superconducting processor

Indistinguishability of particles is a fundamental principle of quantum mechanics. For all elementary and quasiparticles observed to date - including fermions, bosons, and Abelian anyons - this principle guarantees that the braiding of identical particles leaves the system unchanged. However, in two spatial dimensions, an intriguing possibility exists: braiding of non-Abelian anyons causes rotations in a space of topologically degenerate wavefunctions. Hence, it can change the observables of the system without violating the principle of indistinguishability. Despite the well developed mathematical description of non-Abelian anyons and numerous theoretical proposals, the experimental observation of their exchange statistics has remained elusive for decades. Controllable many-body quantum states generated on quantum processors offer another path for exploring these fundamental phenomena. While efforts on conventional solid-state platforms typically involve Hamiltonian dynamics of quasi-particles, superconducting quantum processors allow for directly manipulating the many-body wavefunction via unitary gates. Building on predictions that stabilizer codes can host projective non-Abelian Ising anyons, we implement a generalized stabilizer code and unitary protocol to create and braid them. This allows us to experimentally verify the fusion rules of the anyons and braid them to realize their statistics. We then study the prospect of employing the anyons for quantum computation and utilize braiding to create an entangled state of anyons encoding three logical qubits. Our work provides new insights about non-Abelian braiding and - through the future inclusion of error correction to achieve topological protection - could open a path toward fault-tolerant quantum computing

Alterations in central catecholamines associated with immune responding in adult and aged mice

Central catecholamine alterations associated with immune activity are similar to those seen following stressor exposure. Inasmuch as aged animals exhibit more pronounced stressor-provoked alterations of central amines relative to younger animals, it was of interest to determine whether immune challenge would similarly induce more pronounced central amine variations in older animals. Fifteen-month old CD-1 mice challenged with 107 sheep red blood cells (SRBC) revealed an equivalent peak splenic plaque-forming cell response (4 days after antigen challenge) to that of 3-month-old mice challenged with 106 cells. Neither plasma adrenocorticotropic hormone (ACTH) nor corticosterone levels varied over days following immunization, although ACTH levels were generally higher in the older mice. In both age groups reductions of hypothalamic and locus coeruleus norepinephrine (NE) and increased accumulation of the metabolite MHPG coincided with (or preceded by 24 h) the peak immune response. However, increased accumulation of MHPG in the hypothalamus was greater and occurred earlier in the locus coeruleus of the aged mice. Likewise, at or about the time of peak immune responses nucleus accumbens dopamine (DA) levels were reduced and metabolites elevated in both age groups, while in the prefrontal cortex only DA metabolite levels were elevated. These data are commensurate with previous findings showing that SRBC inoculation may influence central neurotransmitters and that such effects correspond with the time of the peak immune responses. Moreover, in so far as hypothalamic NE utilization is concerned, it seems that the effects of SRBC inoculation are more pronounced in aged animals