52 research outputs found
Hybrid variational quantum eigensolvers: merging computational models
Variational quantum eigensolvers (VQEs) are a highly successful technique for
simulating physical models on quantum computers. Recently, they were extended
to the measurement-based approach of quantum computing, bringing the strengths
and advantages of this computational model to VQEs. In this work, we push the
design and integration frontiers of VQE further by blending measurement-based
elements into the gate-based paradigm to form a hybrid VQE. This facilitates
the design of a problem-informed variational ansatz and also allows the
efficient implementation of many-body Hamiltonians on NISQ devices. We
experimentally demonstrate our approach on a superconducting quantum computer
by investigating the perturbed planar code, Z2 and SU(3) lattice gauge
theories, and the LiH molecule.Comment: 5+18 pages, 2+4 figure
SQEM: Superposed Quantum Error Mitigation
Overcoming the influence of noise and imperfections is one of the main
challenges in quantum computing. Here, we present an approach based on applying
a desired unitary computation in superposition, either on the system of
interest or some auxiliary states. We demonstrate that parallel applications of
the same operation lead to significant noise mitigation when arbitrary noise
processes are considered. We first design probabilistic implementations of our
scheme. These are plug-and-play, are independent of the noise characteristic
and require no post-processing. We then show that the success probability can
be enhanced (up to deterministic) using adaptive corrections. We provide an
analytical study of our protocol performance and demonstrate that unit fidelity
can be achieved asymptotically. The approaches introduced are suitable to both
standard gate-based (GB) and measurement-based (MB) computational models.Comment: 4+ pages, 3 figure
Enhancing Quantum Computation via Superposition of Quantum Gates
Overcoming the influence of noise and imperfections in quantum devices is one
of the main challenges for viable quantum applications. In this article, we
present different protocols, which we denote as "superposed quantum error
mitigation" (SQEM), that enhance the fidelity of single gates or entire
computations by performing them in coherent superposition. Our results
demonstrate that via our methods, significant noise suppression can be achieved
for most kinds of decoherence and standard experimental parameter regimes. Our
protocols can be either deterministic, such that the outcome is never
post-selected, or probabilistic, in which case the resulting state must be
discarded unless a well-specified condition is met. By using sufficiently many
resources and working under broad assumptions, our methods can yield the
desired output state with unit fidelity. Finally, we analyze our approach for
gate-based, measurement-based and interferometric-based models, demonstrating
the applicability in all cases and investigating the fundamental mechanisms
they rely upon.Comment: 38 pages, 15 figure
A resource efficient approach for quantum and classical simulations of gauge theories in particle physics
Gauge theories establish the standard model of particle physics, and lattice
gauge theory (LGT) calculations employing Markov Chain Monte Carlo (MCMC)
methods have been pivotal in our understanding of fundamental interactions. The
present limitations of MCMC techniques may be overcome by Hamiltonian-based
simulations on classical or quantum devices, which further provide the
potential to address questions that lay beyond the capabilities of the current
approaches. However, for continuous gauge groups, Hamiltonian-based
formulations involve infinite-dimensional gauge degrees of freedom that can
solely be handled by truncation. Current truncation schemes require
dramatically increasing computational resources at small values of the bare
couplings, where magnetic field effects become important. Such limitation
precludes one from `taking the continuous limit' while working with finite
resources. To overcome this limitation, we provide a resource-efficient
protocol to simulate LGTs with continuous gauge groups in the Hamiltonian
formulation. Our new method allows for calculations at arbitrary values of the
bare coupling and lattice spacing. The approach consists of the combination of
a Hilbert space truncation with a regularization of the gauge group, which
permits an efficient description of the magnetically-dominated regime. We focus
here on Abelian gauge theories and use dimensional quantum
electrodynamics as a benchmark example to demonstrate this efficient framework
to achieve the continuum limit in LGTs. This possibility is a key requirement
to make quantitative predictions at the field theory level and offers the
long-term perspective to utilise quantum simulations to compute physically
meaningful quantities in regimes that are precluded to quantum Monte Carlo.Comment: 25 pages, 9 figures, journal versio
Towards simulating 2D effects in lattice gauge theories on a quantum computer
Gauge theories are the most successful theories for describing nature at its
fundamental level, but obtaining analytical or numerical solutions often
remains a challenge. We propose an experimental quantum simulation scheme to
study ground state properties in two-dimensional quantum electrodynamics (2D
QED) using existing quantum technology. The proposal builds on a formulation of
lattice gauge theories as effective spin models in arXiv:2006.14160, which
reduces the number of qubits needed by eliminating redundant degrees of freedom
and by using an efficient truncation scheme for the gauge fields. The latter
endows our proposal with the perspective to take a well-controlled continuum
limit. Our protocols allow in principle scaling up to large lattices and offer
the perspective to connect the lattice simulation to low energy observable
quantities, e.g. the hadron spectrum, in the continuum theory. By including
both dynamical matter and a non-minimal gauge field truncation, we provide the
novel opportunity to observe 2D effects on present-day quantum hardware. More
specifically, we present two Variational Quantum Eigensolver (VQE) based
protocols for the study of magnetic field effects, and for taking an important
first step towards computing the running coupling of QED. For both instances,
we include variational quantum circuits for qubit-based hardware, which we
explicitly apply to trapped ion quantum computers. We simulate the proposed VQE
experiments classically to calculate the required measurement budget under
realistic conditions. While this feasibility analysis is done for trapped ions,
our approach can be easily adapted to other platforms. The techniques presented
here, combined with advancements in quantum hardware pave the way for reaching
beyond the capabilities of classical simulations by extending our framework to
include fermionic potentials or topological terms
Reinterpretation in visual imagery is possible without visual cues: a validation of previous research
Sexual Functioning and Opioid Maintenance Treatment in Women. Results From a Large Multicentre Study
Opioid maintenance treatment (OMT) is the most widespread therapy for both females and males opioid addicts. While many studies have evaluated the OMT impact on men’s sexuality, the data collected about the change in women’s sexual functioning is still limited despite the fact that it is now well-known that opioids - both endogenous and exogenous - affect the endocrine system and play an important role in sexual functioning. The present study aims to determine how OMT with buprenorphine (BUP) or methadone (MTD) affects sexual health in women; examining also any possible emerging correlation between sexual dysfunction (SD), type of opioid and patients’ mental health. This multi-center study case recruited 258 female volunteers attending Italian public Addiction Outpatients Centers that were stabilized with OMT for at least 3 months. SD was assessed with the Arizona Sexual Experience Scale. The twelve-item General Health Questionnaire was used to assess participants’ mental health conditions. The results show that 56.6% of women receiving OMT for at least 3 months presented SD without significant differences between MTD e BUP groups. The majority of the subjects with SD have a poorer quality of intimate relationships and worse mental health than the average. To the best of our knowledge, the present study is the largest report on the presence of SDs in women as a side effects of MTD and BUP used in OMT. Since SDs cause difficulties in intimate relationships, lower patients’ quality of life and interfere with OMT beneficial outcomes, we recommend that women undertaking an opioid therapy have routine screening for SD and we highlight the importance to better examine opioid-endocrine interactions in future studies in order to provide alternative potential treatments such as the choice of opioid, opioid dose reduction and hormone supplementation
Visual selective attention and reading efficiency are related in children
We investigated the relationship between visual selective attention and linguistic performance. Subjects were classified in four categories according to their accuracy in a letter cancellation task involving selective attention. The task consisted in searching a target letter in a set of background letters and accuracy was measured as a function of set size. We found that children with the lowest performance in the cancellation task present a significantly slower reading rate and a higher number of reading visual errors than children with highest performance. Results also show that these groups of searchers present significant differences in a lexical search task whereas their performance did not differ in lexical decision and syllables control task.
The relationship between letter search and reading, as well as the finding that poor readers-searchers perform poorly lexical search tasks also involving selective attention, suggest that the relationship between letter search and reading difficulty may reflect a deficit in a visual selective attention mechanisms which is involved in all these tasks.
A deficit in visual attention can be linked to the problems that disabled readers present in the function of magnocellular stream which culminates in posterior parietal cortex, an area which plays an important role in guiding visual attention
Fisiopatologia dell'osso
L’osso è un tessuto metabolicamente attivo che cresce e si modella sotto l’influenza di forze meccaniche e stimoli ormonali e biochimici che con l’età ne modificano dimensioni e superficie. L’infanzia e l’adolescenza sono caratterizzate da un rilevante aumento della massa ossea insieme ad una progressiva crescita non solo in senso longitudinale, ma anche nelle dimensioni e forma delle ossa e questo viene attuato grazie al complesso processo del rimodellamento osseo.
Tale procedimento è il risultato di due opposte attività cellulari, la neoformazione e il riassorbimento, attuate rispettivamente dagli osteoblasti e dagli osteoclasti
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