28 research outputs found
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
Evaluating the Solvent Stark Effect from Temperature-Dependent Solvatochromic Shifts of Anthracene
The solvent Stark effect on the spectral shifts of anthracene is studied with temperature‐dependent solvatochromic measurements. The Stark contribution ΔvStark to the absorption shift Δvp in polar solvents is measured to be ΔvStark=(53±35) cm−1, in reasonable agreement with dielectric continuum theory estimate of 28 cm−1, whereas the major shift Δvp∼300 cm−1 presumably originates from the solute quadrupole. We pay attention to the accurate correction of Δvp for the nonpolar contribution that is crucial when the shifts are modest in magnitude.Peer Reviewe
Correction to Organometallic Complexes of Graphene: Toward Atomic Spintronics Using a Graphene Web
Multistate Multiconfiguration Quantum Chemical Computation of the Two-Photon Absorption Spectra of Bovine Rhodopsin
Recently, progress in IR sources has led to the discovery that humans can detect infrared (IR) light. This is hypothesized to be due to the two-photon absorption (TPA) events promoting the retina dim-light rod photoreceptor rhodopsin to the same excited state populated via one-photon absorption (OPA). Here, we combine quantum mechanics/molecular mechanics and extended multiconfiguration quasi-degenerate perturbation theory calculations to simulate the TPA spectrum of bovine rhodopsin (Rh) as a model for the human photoreceptor. The results show that the TPA spectrum of Rh has an intense S-0 -> S-1 band but shows also S-0 -> S-2 and S-0 -> S-3 transitions whose intensities, relative to the S-0 -> S-1 band, are significantly increased when compared to the corresponding bands of the OPA spectrum. In conclusion, we show that IR light in the 950 nm region can be perceived by rod photoreceptors, thus supporting the two-photon origin of the IR perception. We also found that the same photoreceptor can perceive red (i.e., close to 680 nm) light provided that TPA induces population of S-2
Trifluoromethylation of Fullerenes: Kinetic and Thermodynamic Control
We present a survey and theoretical
interpretation of the experimental
results on trifluoromethylation of fullerenes. A thermodynamic model
has been developed to describe the C<sub>60/70</sub>(CF<sub>3</sub>)<sub><i>n</i></sub> condensed phase mixtures capable of
free exchange of addends and, consequently, of isomerization and changing
the degrees of addition. It was found that the purely thermodynamic
model affords at least satisfactory prediction of composition of products
even for apparently nonequilibrium syntheses. Special cases can be
identified by means of detailed kinetic modeling based on the BEP
approach, which includes stepwise energetic analysis of the possible
trifluoromethylation sequences. This analysis reveals two types of
reactions with remarkable difference in rates: direct trifluoromethylation
and rearrangements of the CF<sub>3</sub> groups. Whenever a particular
group of compounds is interrelated through direct addition/abstraction
of CF<sub>3</sub> groups, it is more or less safe to assume that the
said group is in equilibrium describable by the thermodynamic model.
In the same time, the slower migration of addends is controlled kinetically,
and interference of the sublimation processes frequently prevents
its equilibration. Among the most illustrative examples of hindered
formation via rearrangements in absence of sufficiently favorable
direct trifluoromethylation pathways are certain isomers of the <i>C</i><sub>3<i>v</i></sub>–C<sub>60</sub>(CF<sub>3</sub>)<sub>18</sub>, C<sub>70</sub>(CF<sub>3</sub>)<sub>18</sub>, and C<sub>70</sub>(CF<sub>3</sub>)<sub>20</sub> compounds
Anion Radicals of Isomeric [5,6] and [6,6] Benzoadducts of Sc<sub>3</sub>N@C<sub>80</sub>: Remarkable Differences in Endohedral Cluster Spin Density and Dynamics
The
anion radicals of isomeric [5,6] and [6,6] Sc<sub>3</sub>N@C<sub>80</sub> benzoadducts were studied by electron spin resonance spectroscopy,
density functional theory computations, and molecular dynamics. In
both compounds the rotation of the Sc<sub>3</sub>N cluster is frozen
and the spin density distribution of the cluster is highly anisotropic,
with hyperfine coupling constants of 9.1 and 2 × 33.3 G for the
[5,6] adduct and ∼0.6 and 2 × 47.9 G for the [6,6] adduct.
Remarkably, the subtle variation of the position of the exohedral
group on the surface of the cage results in very pronounced changes
in the spin density distribution and the dynamics of the encapsulated
Sc<sub>3</sub>N cluster
Cage Shrinkage of Fullerene via a C<sub>2</sub> Loss: from IPR C<sub>90</sub>(28)Cl<sub>24</sub> to Nonclassical, Heptagon-Containing C<sub>88</sub>Cl<sub>22/24</sub>
A new
case of chlorination-promoted fullerene cage shrinkage is reported.
Chlorination of C<sub>90</sub> (isolated pentagon rule isomer no.
28) with VCl<sub>4</sub> afforded C<sub>88</sub>Cl<sub>22</sub> with
a nonclassic carbon cage (NCC) containing 1 heptagon and 13 pentagons
including 2 fused pairs flanking the heptagon. The pathway of C<sub>2</sub> abstraction from the C<sub>90</sub> cage is suggested on
the basis of density functional theory calculations
Skeletal Transformation of Isolated Pentagon Rule (IPR) Fullerene C<sub>82</sub> into Non-IPR C<sub>82</sub>Cl<sub>28</sub> with Notably Low Activation Barriers
A novel case of chlorination-promoted skeletal transformation
in
higher fullerenes is reported. Chlorination of C<sub>82</sub> [isolated
pentagon rule (IPR) isomer no. 3] with SbCl<sub>5</sub> results in
two consecutive Stone–Wales rearrangements into non-IPR C<sub>82</sub>Cl<sub>28</sub> with one pair of fused pentagons. An extensive
theoretical study of the transformation pathways in C<sub>82</sub> revealed that the thermodynamically favorable rearrangement into
non-IPR C<sub>82</sub>Cl<sub>28</sub> needs a comparatively low activation
energy