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Sunho Kim

Publications and source records attributed to Sunho Kim.

28 records · Page 2Linked to original sources
arXiv2021

Protocol for unambiguous quantum state discrimination using quantum coherence

Roa et al. showed that quantum state discrimination between two nonorthogonal quantum states does not require quantum entanglement but quantum dissonance only. We find that quantum coherence can also be utilized for unambiguous quantum state discrimination. We present a protocol and quantify the required coherence for this task. We discuss the optimal unambiguous quantum state discrimination strategy in some cases. In particular, our work illustrates an avenue to find the optimal strategy for discriminating two nonorthogonal quantum states by measuring quantum coherence.

quant-ph↗
arXiv2021

Quantifying dynamical coherence with coherence measures

Quantum coherence, like entanglement, is a fundamental resource in quantum information. In recent years, remarkable progress has been made in formulating resource theory of coherence from a broader perspective. The notions of block-coherence and POVM-based coherence have been established. Certain challenges, however, remain to be addressed. It is difficult to define incoherent operations directly, without requiring incoherent states, which proves a major obstacle in establishing the resource theory of dynamical coherence. In this paper, we overcome this limitation by introducing an alternate definition of incoherent operations, induced via coherence measures, and quantify dynamical coherence based on this definition. Finally, we apply our proposed definition to quantify POVM-based dynamical coherence.

quant-ph↗
arXiv2021

Converting coherence based on positive-operator-valued measures into entanglement

Quantum resource theories provide a diverse and powerful framework for extensively studying the phenomena in quantum physics. Quantum coherence, a quantum resource, is the basic ingredient in many quantum information tasks. It is a subject of broad and current interest in quantum information, and many new concepts have been introduced and generalized since its establishment. Here we show that the block coherence can be transformed into entanglement via a block incoherent operation. Moreover, we find that the POVM-based coherence associated with block coherence through the Naimark extension acts as a potential resource from the perspective of generating entanglement. Finally, we discuss avenues of creating entanglement from POVM-based coherence, present strategies that require embedding channels and auxiliary systems, give some examples, and generalize them.

quant-ph↗
arXiv2020

Synthesis of Brain Tumor MR Images for Learning Data Augmentation

Medical image analysis using deep neural networks has been actively studied. Deep neural networks are trained by learning data. For accurate training of deep neural networks, the learning data should be sufficient, of good quality, and should have a generalized property. However, in medical images, it is difficult to acquire sufficient patient data because of the difficulty of patient recruitment, the burden of annotation of lesions by experts, and the invasion of patients' privacy. In comparison, the medical images of healthy volunteers can be easily acquired. Using healthy brain images, the proposed method synthesizes multi-contrast magnetic resonance images of brain tumors. Because tumors have complex features, the proposed method simplifies them into concentric circles that are easily controllable. Then it converts the concentric circles into various realistic shapes of tumors through deep neural networks. Because numerous healthy brain images are easily available, our method can synthesize a huge number of the brain tumor images with various concentric circles. We performed qualitative and quantitative analysis to assess the usefulness of augmented data from the proposed method. Intuitive and interesting experimental results are available online at https://github.com/KSH0660/BrainTumor

eess.IV↗
arXiv2018

Interrelation between Partial Coherence and Quantum Correlations

Both coherence and entanglement stem from the superposition principle, capture quantumness of a physical system, and play a central role in quantum physics. In a multipartite quantum system, coherence and quantum correlations are closely connected. In particular, it has been established that quantum coherence of a bipartite state is an important resource for its conversion to entanglement [A. Streltsov {\it et al.}, Phys. Rev. Lett. {\bf 115}, 020403 (2015)] and to quantum discord [J. Ma {\it et al}., Phys. Rev. Lett. {\bf 116}, 160407 (2016)]. We show here that there is a very close association between partial coherence introduced by Luo and Sun [S. Luo and Y. Sun, Phys. Rev. A {\bf 96}, 022136 (2017)] and quantum correlations (quantified by quantum discord) in both directions. Furthermore, we propose families of coherence measures in terms of quantum correlations and quantum Fisher information.

quant-ph↗
arXiv2018

Characterizing nonclassical correlations via local quantum Fisher information

We define two ways of quantifying the quantum correlations based on quantum Fisher information (QFI) in order to study the quantum correlations as a resource in quantum metrology. By investigating the hierarchy of measurement-induced Fisher information introduced in Lu et al. [X. M. Lu, S. Luo, and C. H. Oh, Phys Rev. A 86, 022342 (2012)], we show that the presence of quantum correlation can be confirmed by the difference of the Fisher information induced by the measurements of two hierarchies. In particular, the quantitative quantum correlations based on QFI coincide with the geometric discord for pure quantum states.

quant-ph↗
arXiv2017

Logically reversible measurements: Construction and application

We show that for any von Neumann measurement, we can construct a logically reversible measurement such that Shannon entropies and quantum discords induced by the two measurements have compact connections. In particular, we prove that quantum discord for the logically reversible measurement is never less than that for the von Neumann measurement.

quant-ph↗
arXiv2017

The Decomposition Properties of Quantum Discord

The quantum discord was introduced by Ollivier, Zurek, Henderson and Vedral as an indicator of the degree of quantumness of mixed states. In this paper, we give out the decomposition condition of quantum discords. Moreover, we show that under the condition, the quantum correlations between the quantum systems can be captured completely by the entanglement measure.

quant-ph↗
arXiv2011

Coverage Control of Silica-Assisted Grown DNA Crystals

One of the main goals of DNA nanotechnology is to provide a viable solution to the limitations of top-down approaches in microfabrication schemes. Although a completely practical bottom-up approach is yet to be realized, there has been great progress in integrating the two approaches in the past few years. In this vein, we present a novel surface assisted fabrication scheme able to directly control the coverage rate, from 0 to 100%, of functionalized DNA nanostructures on centimeter-scaled silica (SiO_2) substrates which is one key to harnessing DNA's unique properties in electronics and photonics. Furthermore, electrostatic interactions between the DNA structures and the surface lead to dramatic topological changes of the structures, creating novel formations of the crystals. These results provide a direct route to applying fully functionalized layers of DNA nanostructures to current technologies in SiO_2-based electronics and photonics.

cond-mat.mtrl-sci↗