59 research outputs found
Skeleton-based Action Recognition of People Handling Objects
In visual surveillance systems, it is necessary to recognize the behavior of
people handling objects such as a phone, a cup, or a plastic bag. In this
paper, to address this problem, we propose a new framework for recognizing
object-related human actions by graph convolutional networks using human and
object poses. In this framework, we construct skeletal graphs of reliable human
poses by selectively sampling the informative frames in a video, which include
human joints with high confidence scores obtained in pose estimation. The
skeletal graphs generated from the sampled frames represent human poses related
to the object position in both the spatial and temporal domains, and these
graphs are used as inputs to the graph convolutional networks. Through
experiments over an open benchmark and our own data sets, we verify the
validity of our framework in that our method outperforms the state-of-the-art
method for skeleton-based action recognition.Comment: Accepted in WACV 201
Nearly Deterministic Bell Measurement for Multiphoton Qubits and Its Application to Quantum Information Processing
We propose a Bell measurement scheme by employing a logical qubit in
Greenberger-Horne-Zeilinger (GHZ) entanglement with an arbitrary number of
photons. Remarkably, the success probability of the Bell measurement as well as
teleportation of the GHZ entanglement can be made arbitrarily high using only
linear optics elements and photon on-off measurements as the number of photons
increases. Our scheme outperforms previous proposals using single photon qubits
when comparing the success probabilities in terms of the average photon usages.
It has another important advantage for experimental feasibility that it does
not require photon number resolving measurements. Our proposal provides an
alternative candidate for all-optical quantum information processing.Comment: 7 pages (including supplementary material), 2 figures, to be
published in Phys. Rev. Let
Entangled coherent states versus entangled photon pairs for practical quantum information processing
We compare effects of decoherence and detection inefficiency on entangled
coherent states (ECSs) and entangled photon pairs (EPPs), both of which are
known to be particularly useful for quantum information processing (QIP). When
decoherence effects caused by photon losses are heavy, the ECSs outperform the
EPPs as quantum channels for teleportation both in fidelities and in success
probabilities. On the other hand, when inefficient detectors are used, the
teleportation scheme using the ECSs suffers undetected errors that result in
the degradation of fidelity, while this is not the case for the teleportation
scheme using the EPPs. Our study reveals the merits and demerits of the two
types of entangled states in realizing practical QIP under realistic
conditions.Comment: 9 pages, 6 figures, substantially revised version, to be published in
Phys. Rev.
Efficient quantum simulation of nonlinear interactions using SNAP and Rabi gates
Quantum simulations provide means to probe challenging problems within
controllable quantum systems. However, implementing or simulating deep-strong
nonlinear couplings between bosonic oscillators on physical platforms remains a
challenge. We present a deterministic simulation technique that efficiently and
accurately models nonlinear bosonic dynamics. This technique alternates between
tunable Rabi and SNAP gates, both of which are available on experimental
platforms such as trapped ions and superconducting circuits. Our proposed
simulation method facilitates high-fidelity modeling of phenomena that emerge
from higher-order bosonic interactions, with an exponential reduction in
resource usage compared to other techniques. We demonstrate the potential of
our technique by accurately reproducing key phenomena and other distinctive
characteristics of ideal nonlinear optomechanical systems. Our technique serves
as a valuable tool for simulating complex quantum interactions, simultaneously
paving the way for new capabilities in quantum computing through the use of
hybrid qubit-oscillator systems
Controllability-Aware Unsupervised Skill Discovery
One of the key capabilities of intelligent agents is the ability to discover
useful skills without external supervision. However, the current unsupervised
skill discovery methods are often limited to acquiring simple, easy-to-learn
skills due to the lack of incentives to discover more complex, challenging
behaviors. We introduce a novel unsupervised skill discovery method,
Controllability-aware Skill Discovery (CSD), which actively seeks complex,
hard-to-control skills without supervision. The key component of CSD is a
controllability-aware distance function, which assigns larger values to state
transitions that are harder to achieve with the current skills. Combined with
distance-maximizing skill discovery, CSD progressively learns more challenging
skills over the course of training as our jointly trained distance function
reduces rewards for easy-to-achieve skills. Our experimental results in six
robotic manipulation and locomotion environments demonstrate that CSD can
discover diverse complex skills including object manipulation and locomotion
skills with no supervision, significantly outperforming prior unsupervised
skill discovery methods. Videos and code are available at
https://seohong.me/projects/csd/Comment: ICML 202
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Optimal Estimation of Conjugate Shifts in Position and Momentum by Classically Correlated Probes and Measurements
Multiparameter estimation is necessary for force sensing due to simultaneous and nontrivial small changes of position and momentum. The design of quantum probes that allow simultaneous estimation of all parameters is therefore an important task. The optimal methods for estimation of the conjugate changes of position and momentum of quantum harmonic oscillator employ probes in entangled or quantum non-Gaussian states. We show that the same results can be obtained in a significantly more feasible fashion by employing independent sets of differently squeezed Gaussian states classically correlated with position or momentum measurements. This result demonstrates an unexplored power of a classical correlation between the probe states and measurements directly applicable to force sensing
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