Optimal Fidelity Research Articles

Data-Driven Playback of Natural Tactile Texture Via Broadband Friction Modulation.

We used broadband electroadhesion to reproduce the friction force profile measured as a finger slid across a textured surface. In doing so, we were also able to reproduce with high fidelity the skin vibrations characteristic of that texture; however, we found that this did not reproduce the original perception. To begin, the reproduction felt weak. In order to maximize perceptual similarity between a real texture and its friction force playback, the vibratory magnitude of the latter must be scaled up on average ≈ 3X for fine texture and ≈ 5X for coarse texture samples. This additional gain appears to correlate with perceived texture roughness. Additionally, even with optimal scaling and high fidelity playback, subjects could identify which of two reproductions corresponds to a real texture with only 71 % accuracy, as compared to 95 % accuracy when using real texture alternatives. We conclude that while tribometry and vibrometry data can be useful for texture classification, they appear to contribute only partially to texture perception. We propose that spatially distributed excitation of skin within the fingerpad may play an additional key role, and may thus be able to contribute to high fidelity texture reproduction.

Deterministic transformations between unitary operations: Exponential advantage with adaptive quantum circuits and the power of indefinite causality

This work analyses the performance of quantum circuits and general processes to transformkuses of an arbitrary unitary operationUinto another unitary operationf(U). When the desired functionfa homomorphism, i.e.,f(UV)=f(U)f(V), it is known that optimal average fidelity is attainable by parallel circuits and indefinite causality does not provide any advantage. Here we show that the situation changes dramatically when considering anti-homomorphisms, i.e.,f(UV)=f(V)f(U). In particular, we prove that whenfis an anti-homomorphism, sequential circuits could exponentially outperform parallel ones and processes with indefinite causal order could outperform sequential ones. We presented explicit constructions on how to obtain such advantages for the unitary inversion taskf(U)=U−1and the unitary transposition taskf(U)=UT. We also stablish a one-to-one connection between the problem of unitary estimation and parallel unitary transposition, allowing one to easily translate results from one field to the other. Finally, we apply our results to several concrete problem instances and present a method based on computer-assisted proofs to show optimality.

Improving entanglement of even entangled coherent states via superposition of number-conserving operations

A scheme for improving entanglement is proposed by repeatedly performing number-conserving generalized superposition of products (GSP) operation, i.e., saa†+ta†am with s2+t2=1, on each modes of even entangled coherent state (EECS). Both Einstein–Podolsky–Rosen (EPR) correlation and concurrence are used as the measures for describing entanglement. It is found that both single-mode and two-mode-symmetric GSP operations can be used for the entanglement improvement. In particular, for the optimal EPR correlation, the GSP-EECS with two-mode-symmetric first-order operations presents a better performance for the entanglement improvement than the cases of high-order GSP operations. Compared to several special non-Gaussian operations, including photon subtraction-then-addition (PSTA) (s=0) and photon-addition-then-subtraction (PATS) (s=1), it is shown that the entanglement of GSP-EECS is always superior to those of both PSTA-EECS and PATS-EECS at a small amplitude level. When the GSP-EECS is used as the entangled resource for teleportation, our optimal teleportation fidelity presents the best performance.

Overlapping effect in dense all-optical, point-by-point recording of holographic patterns in the ferrimagnetic alloy

Ferrimagnetic alloys are promising media for the ultrafast, non-volatile recording of diffractive patterns for further development of computer-generated holography toward practical display applications. In this work we measure and analyze the influence of the overlapping effect during dense point-by-point recording of holographic patterns on the quality of their far field reconstructions. In particular, we numerically and experimentally derive the optimal degree of overlapping of the holographic points being written in GdFeCo alloys for the optimal fidelity of reconstructed 2-D images, which features unitary fill factor of the writing process.

A novel fidelity selection strategy-guided multifidelity kriging algorithm for structural reliability analysis

Multifidelity (MF) surrogate models have recently attracted intensive attention due to their advantage of reducing computational demand by fusing multiple sources of data. However, their applications in reliability analyses with active learning processes are scarce because of lack of effective strategies for determining locations and fidelities of updated samples. To circumvent this bottleneck, a new active learning-based MF kriging method for reliability analysis via RU learning function and “BSC-Believer” fidelity selection strategy is proposed. The proposed approach employs a two-phase operation to determine location and fidelity of the updated sample in each iteration. In the first stage, the location of the updated sample is ascertained via learning function RU, which has excellent performance regarding the tradeoff between exploration and exploitation. Then, the “BSC-Believer” strategy is introduced by combining the estimated relative error of the failure probability, the kriging believer concept, and a cost function to select the optimal fidelity for updating. Through the “BSC-Believer” strategy, the appropriate fidelity for reducing failure probability prediction uncertainty within a unit of computational demand is identified. It is demonstrated through five examples that the proposed algorithm is superior to the recently reported approaches in reducing the computational burden of maintaining the desired estimation accuracy.

Temporal shaping of single photons by engineering exciton dynamics in a single quantum dot

The majority of photonic quantum information technologies rely on single photons that have high purity and indistinguishability. Although solid-state quantum emitters can serve such single photons on demand, their asymmetric temporal and spatial mode profiles limit the optimal efficiency and fidelity of quantum interaction. Here, we demonstrate single-photon pulses at a telecom wavelength with a Gaussian-like temporal mode profile from a cavity-coupled single quantum dot. Engineering the exciton dynamics via multi-exciton cascade recombination and cavity detuning enables us to modify the rise and decay dynamics of single excitons. Furthermore, the cascade recombination process temporally retards the single-exciton emission from the background emission, leading to possible purification of single photons at high excitation power. In addition, coupling quantum dots into a low Q cavity mode leads to a Gaussian-like spatial mode profile, which brings a high collection efficiency. This approach paves the way for producing single photons with an optimized temporal and spatial waveform.

Efficient entanglement distillation for quantum channels with polarization mode dispersion

Quantum entanglement shared by remote network nodes serves as a valuable resource for promising applications in distributed computing, cryptography, and sensing. However, distributing high-quality entanglement via fiber-optic routes could be challenging due to the various decoherence mechanisms in fibers. In particular, one of the primary polarization decoherence mechanisms in optical fibers is polarization mode dispersion (PMD), which is the distortion of optical pulses by randomly varying birefringences. To mitigate the effect of decoherence in entangled particles, quantum entanglement distillation (QED) algorithms have been proposed. One particular class, the recurrence QED algorithms, stands out because it has relatively relaxed requirements both on the size of the quantum circuits involved and on the initial quality of entanglement between particles. However, because the number of required particles grows exponentially with the number of distillation rounds, an efficient recurrence algorithm needs to converge quickly. We present a recurrence QED algorithm designed for photonic qubit pairs affected by PMD-degraded channels. Our proposed algorithm achieves the optimal fidelity as well as the optimal success probability (conditioned on the fact that optimal fidelity is achieved) in every round of distillation. The attainment of the maximal fidelity improves the convergence speed of fidelity with respect to the number of distillation rounds from linear to quadratic and, hence, significantly reduces the number of rounds. Combined with the fact that the optimal success probability is achieved, the proposed algorithm provides an efficient method to distribute entangled states with a high fidelity via optical fibers.

Experimental demonstration of entanglement-enabled universal quantum cloning in a circuit

No-cloning theorem forbids perfect cloning of an unknown quantum state. A universal quantum cloning machine (UQCM), capable of producing two copies of any input qubit with the optimal fidelity, is of fundamental interest and has applications in quantum information processing. This is enabled by delicately tailored nonclassical correlations between the input qubit and the copying qubits, which distinguish the UQCM from a classical counterpart, but whose experimental demonstrations are still lacking. We here implement the UQCM in a superconducting circuit and investigate these correlations. The measured entanglements well agree with our theoretical prediction that they are independent of the input state and thus constitute a universal quantum behavior of the UQCM that was not previously revealed. Another feature of our experiment is the realization of deterministic and individual cloning, in contrast to previously demonstrated UQCMs, which either were probabilistic or did not constitute true cloning of individual qubits.

Comparing fidelity monitoring methods in an evidence-based parenting intervention

Purpose Two common methods in community settings of assessing program fidelity, a critical implementation component for program effectiveness, are video and audio recordings of sessions. This paper aims to examine how these two methods compared when used for a home-based behavioral parenting-training model (SafeCare®). Design/methodology/approach Twenty-five SafeCare video-recorded sessions between home visitors and parents were scored by trained raters either using the video or audio-only portions of recordings. Sessions were coded using fidelity checklists, with items (n = 33) classified as one of two fidelity aspects, content [delivery of program components (n = 15)], or process [communication and rapport building (n = 11)]. Seven items were considered to overlap between constructs. Items were coded as having been done or not done appropriately. Coders rated items as “technological limitation” when scoring methods hindered coding. Analyses compared percent agreement and disagreement between audio and video coders. Findings Overall agreement between coders was 72.12%. Levels of agreement were higher for content items (M = 80.89%, SD = 19.68) than process items (58.54%, SD = 34.41). Disagreements due to technology limitations among audio coders were noted among 15 items; particularly, higher levels of disagreement were seen among process items (42.42%) than content items (9.64%). Originality/value Compared to video, fidelity monitoring via audio recordings was associated with some loss of process-related fidelity. However, audio recordings could be sufficient with supplements such as participant surveys, to better capture process items. Research should also examine how content and process fidelity relate to changes in family behavior to further inform optimal fidelity monitoring methods for program use.

Enhancing teleportation of a single-qubit state by the unitary transformation in arbitrary decoherence rate

The proposal of the quantum teleportation(QT) is to transfer an unknown quantum state from one place to another through local operations and classical communication. However, the efficiency of standard QT will be significantly reduced due to the influence of the inevitable noise in environments. In this work, we propose two schemes to improve the efficiency of the QT protocol when quantum channel is subjected to bit-flip or phase-flip noise. We find that the so-called more entanglement means low efficiency in the performance of the standard teleportation protocol, and the optimal fidelity is obtained only by using the appropriate unitary operation. Specially, we show that the optimal averaged fidelity to our schemes is always more than the best classically achievable fidelity 2/3. We also provide a physical explanation of the obtained conclusions and our results will be helpful for improving quantum communication with real implementation.

Rheological behavior and particle alignment of cellulose nanocrystal and its composite hydrogels during 3D printing

Cellulose nanocrystal (CNC) has tremendous potential in chemical, material, and food fields as an attractive green bioresource. We formulated viscoelastic hydrogels composed of anisotropic CNC using an extrusion-based 3D printing technology. We explored the rheological properties and printability of CNC hydrogels with different concentrations (0.5–25 wt%), and quantified the shear-induced self-assembly behavior of CNC during printing. The results showed that 20 wt% CNC hydrogels exhibited optimal print resolution and fidelity, with a high degree of orientation (72 %–73 %) of CNC alignment along the printing direction. It provides quantitative guidelines for the development of 3D printable materials with particle orientation. Furthermore, we prepared two composite hydrogels for 3D printing by blending CNC with high/low methoxy pectin (HMP/LMP). The results revealed that two hydrogels had favorable print fidelity at suitable ratios (CNC: HMP = 2:8, CNC: LMP = 10:5). This provided flexible and sustainable choices for the development of medical tissue engineering.

Morphogenetic systems for resource bounded computation and modeling

A further exploration is presented of recent approaches to morphogenetic processes where geometry and form are fundamental primitives. Prior bottom-up approaches in morphogenetic modeling usually target a specific biological process aiming for optimal fidelity. We take a novel, more integrative and more abstract view of these phenomena and aim at properties such as (computational) universality, homeostasis, self-reproduction or self-healing, in both living and artificial evolving systems with explicit geometric 3D arrangements. We refine the recently introduced model of M systems (for morphogenetic systems) that leverages certain constructs in membrane computing and DNA self-assembly. The model is still based on local interactions of simple atomic components under explicit geometric constraints given by their shapes and spatial arrangements. We demonstrate two types of capabilities of the extended models. First, they are computationally universal in the Turing sense because they can simulate Turing machines very efficiently, with only a linear slowdown factor. Furthermore, they have the theoretical capability to probabilistically solve NP-hard problems in polynomial time. Second, more importantly, they unfold to exhibit certain macro-properties characteristic of living organisms (particularly, the ability of self-assembly of complex structures, self-reproduction and self-healing) as global properties observable at the macro-level, without explicit programming of these properties beyond simple rules of interaction. Besides providing a new theoretical background for this type of model, we provide quantitative evidence of these properties in a simple cell-like M system model. These results have been obtained using an M system simulator and visualizer that is available as open source software for further research in this area.

Deterministic Generation of Large Fock States.

We present a protocol to deterministically prepare the electromagnetic field in a large photon number state. The field starts in a coherent state and, through resonant interaction with one or few two-level systems, it evolves into a coherently displaced Fock state without any postselection. We show the feasibility of the scheme under realistic parameters. The presented method opens a door to reach Fock states, with n∼100 and optimal fidelities above 70%, blurring the line between macroscopic and quantum states of the field.

Two-qubit state recovery from amplitude damping based on weak measurement

In the quantum control process, arbitrary pure or mixed initial states need to be protected from amplitude damping through the noise channel using measurements and quantum control. However, how to achieve it on a two-qubit quantum system remains a challenge. In this paper, we propose a feed-forward control approach to protect arbitrary two-qubit pure or mixed initial states using the weak measurement. A feed-forward operation and measurements are used before the noise channel, and afterwards a reversed operation and measurements are applied to recover the state back to its initial state. In the case of two-qubit pure states, we use the unravelling trick to describe the state of the system in each step of the control procedure. For two-qubit mixed states, a completely-positive trace-preserving (CPTP) map is implemented. Finally, the fidelity and success probability are used to evaluate the effect of protection. The complete recovery conditions for the measurement strengths are derived, under which we achieve the optimal fidelity and the success probability of recovering the initial pure or mixed states.

Nonclassicality and entanglement properties of non-Gaussian entangled states via a superposition of number-conserving operations

We theoretically investigate the nonclassicality and entanglement properties of non-Gaussian entangled states generated by using a number-conserving generalized superposition of products (GSP), i.e., $$\left( saa^{\dag }+ta^{\dag }a\right) ^{m}$$ with $$s^{2}+t^{2}=1$$ on each mode of an input two-mode squeezed coherent (TMSC) state. The simulation results show that, compared to the typical two-mode squeezed vacuum state, the usage of small coherent amplitude is conductive to offering an opportunity for not only effectively enhancing the nonclassicality in terms of antibunching effect and Wigner function, but also significantly improving the entanglement quantified by Einstein–Podolsky–Rosen correlation and Hillery–Zubairy correlation. For the increase of the number of operations, the region of both the existing antibunching effect and the improved entanglement decreases, but this region of the improved teleportation fidelity and the negative distribution of the Wigner function is on the increase. Under an ideal Braunstein and Kimble teleportation protocol, when the generated states are treated as an entangled resource, the optimal teleportation fidelity can be achieved by taking a suitable squeezing parameter and the number of operations for the optimal choices of s. In order to highlight the advantages of the use of the GSP-embedded TMSC, under the same parameters, we also make a comparison about the performances of both the entanglement and the fidelity for different non-Gaussian entangled states, involving the photon-subtracted-then-added TMSC states and the photon-added-then-subtracted TMSC states. It is found that in the regime of small squeezing values, both of the entanglement and the fidelity for the generated states can perform better than the other cases.

High-fidelity Trotter formulas for digital quantum simulation

Quantum simulation promises to address many challenges in fields ranging from quantum chemistry to material science, and high-energy physics, and could be implemented in noisy intermediate-scale quantum devices. A challenge in building good digital quantum simulators is the fidelity of the engineered dynamics given a finite set of elementary operations. Here we present a framework for optimizing the order of operations based on a geometric picture, thus abstracting from the operation details and achieving computational efficiency. Based on this geometric framework, we provide two alternative second-order Trotter expansions, one with optimal fidelity at a short time scale, and the second robust at a long time scale. Thanks to the improved fidelity at different time scale, the two expansions we introduce can form the basis for experimental-constrained digital quantum simulation.

Two-copy quantum teleportation based on GHZ measurement

We investigate quantum teleportation in the two-copy setting based on GHZ measurement and propose the detailed protocol. The output state after the teleportation is analyzed, and the protocol is proved to be trace preserving. The general expression of the optimal teleportation fidelity is derived. The optimal teleportation fidelity is shown to be a linear function of two-copy fully entangled fraction, which is invariant under local unitary transformations. At last, we show two-copy teleportation based on GHZ measurement can be better than one-copy teleportation by an explicit example, which is amenable to demonstration in experiments. Our study is significant for improving the fidelity of teleportation for some limited resource which cannot be significantly distilled. Moreover, it can inspire us to find many other more efficient protocols for teleportation.

Contextual advantage for state-dependent cloning

A number of noncontextual models exist which reproduce different subsets of quantum theory and admit a no-cloning theorem. Therefore, if one chooses noncontextuality as one's notion of classicality, no-cloning cannot be regarded as a nonclassical phenomenon. In this work, however, we show that there are aspects of the phenomenology of quantum state cloning which are indeed nonclassical according to this principle. Specifically, we focus on the task of state-dependent cloning and prove that the optimal cloning fidelity predicted by quantum theory cannot be explained by any noncontextual model. We derive a noise-robust noncontextuality inequality whose violation by quantum theory not only implies a quantum advantage for the task of state-dependent cloning relative to noncontextual models, but also provides an experimental witness of noncontextuality.

Counterdiabatic driving in the quantum annealing of the p -spin model: A variational approach

Finding the exact counterdiabatic potential is, in principle, particularly demanding. Following recent progresses about variational strategies to approximate the counterdiabatic operator, in this paper we apply this technique to the quantum annealing of the $p$-spin model. In particular, for $ p = 3 $ we find a new form of the counterdiabatic potential originating from a cyclic ansatz, that allows us to have optimal fidelity even for extremely short dynamics, independently of the size of the system. We compare our results with a nested commutator ansatz, recently proposed in P. W. Claeys, M. Pandey, D. Sels, and A. Polkovnikov, Phys. Rev. Lett. 123, 090602 (2019), for $ p = 1 $ and $ p = 3 $. We also analyze generalized $ p $-spin models to get a further insight into our ansatz.

A school intervention for 13- to 15-year-olds to prevent dating and relationship violence: the Project Respect pilot cluster RCT

Background ‘Dating and relationship violence’ is intimate partner violence during adolescence. Among dating adolescents in England, 66–75% of girls and 32–50% of boys report victimisation. Multicomponent school-based interventions might reduce dating and relationship violence. We optimised and piloted Project Respect, a new intervention in secondary schools in England, and study methods, to assess the value of a Phase III randomised controlled trial. Objectives To optimise Project Respect and to then conduct a pilot randomised controlled trial in southern England, addressing whether or not progression to a Phase III trial is justified in terms of prespecified criteria. To assess which of two dating and relationship violence scales is optimal, to assess response rates and to consider any necessary refinements. Design Optimisation activities aimed at intervention development and a pilot randomised controlled trial. Setting Optimisation in four secondary schools across southern England, varying by region and local deprivation. A pilot cluster randomised controlled trial in six other such schools (four intervention schools and two control schools), varying by region, attainment and local deprivation. Participants School students in years 8–10 at baseline and staff. Interventions Schools were randomised to the intervention or control arm in a 2 : 1 ratio; intervention comprised staff training, mapping ‘hotspots’ in school for dating and relationship violence, modifying staff patrols, school policy review, informing parents and carers, an application supporting student help-seeking, and a classroom curriculum for students in years 9 and 10 (including student-led campaigns). Main outcome measures Prespecified criteria for progression to Phase III of the trial, concerning acceptability, feasibility, fidelity and response rates. Primary health outcomes were assessed using the Safe Dates and short Conflicts in Adolescent Dating Relationships Inventory measures collected and analysed by individuals who were masked to allocation. Feasibility of economic analysis was assessed. Data sources Baseline and follow-up student and staff surveys, interviews, observations and logbooks. Results The intervention was optimised and approved by the Study Steering Committee. The student response rates in intervention and control groups were 1057 (84.8%) and 369 (76.6%) at baseline, and 1177 (76.8%) and 352 (83.4%) at follow-up, respectively. Safe Dates and the short Conflicts in Adolescent Dating Relationships Inventory had high levels of completion and reliability. At follow-up, prevalence of past-year dating and relationship violence victimisation was around 35% (Safe Dates scale and short Conflicts in Adolescent Dating Relationships Inventory). Staff response rates were very low. Training occurred in all four schools, with suboptimal fidelity. The curriculum was delivered with optimal fidelity in three schools. Other components were delivered inconsistently. Dating and relationship violence was addressed in control schools via violence prevention and responses, but not systematically. Intervention acceptability among students and staff was mixed. An economic evaluation would be feasible. Limitations One school did not undertake baseline surveys. Staff survey response rates were low and completion of the logbook was patchy. Conclusions Our findings suggest that progression to a Phase III trial of this intervention is not indicated because of limited fidelity and acceptability. Future work High prevalence of dating and relationship violence highlights the ongoing need for effective intervention. Potential intervention refinements would include more external support for schools and enhanced curriculum materials. Any future randomised controlled trials could consider having a longer lead-in from randomisation to intervention commencement, using the short Conflicts in Adolescent Dating Relationships Inventory as the primary outcome and not relying on staff surveys. Trial registration Current Controlled Trials ISRCTN65324176. Funding This project was funded by the National Institute for Health Research (NIHR) Public Health Research programme and will be published in full in Public Health Research; Vol. 8, No. 5. See the NIHR Journals Library website for further project information.