arXiv subjects

Jiheon Seong

Publications and source records attributed to Jiheon Seong.

5 recordsLinked to original sources

arXiv2026

Mitigation of Crosstalk Errors in Quantum Measurements

In the present-day quantum information technologies, measurements are performed not only at the end of quantum state evolution but also between quantum circuits to connect short-depth quantum circuits, for instance, variational quantum algorithms. Furthermore, measurements also contain crosstalk errors, which cannot be factorized into individual readout errors. In this work, we investigate methods for mitigating measurement errors across multiple qubits, particularly measurement crosstalk that cannot be corrected by methods for correcting individual readout errors. We present mitigation protocols that generally suppress these errors by up to a percentage level across multiple qubits. We first demonstrate that mitigating measurement errors of individual qubits cannot eliminate measurement crosstalk errors. We then present methods for mitigating measurement readout errors across multiple qubits, accounting for crosstalk noise. Both methods rely on quantum detector tomography. We also present proof-of-principle demonstrations of measurement error mitigation on IBM quantum hardware.

quant-ph↗

arXiv2026

Practical and Efficient Verification of Entanglement with Incomplete Measurement Settings

In this work, we present a practical and efficient framework for verifying entangled states when only a tomographically incomplete measurement setting is available-specifically, when access to observables is severely limited. We show how the experimental estimation of a small number of observables can be directly exploited to construct a large family of entanglement witnesses, enabling the efficient identification of entangled states. Moreover, we introduce an optimization approach, formulated as a semidefinite program, that systematically searches for those witnesses best suited to reveal entanglement under the given measurement constraints. We demonstrate the practicality of the approach in a proof-of-principle experiment with photon-polarization qubits, where entanglement is certified using only a fraction of the full measurement data. These results reveal the maximal usefulness of incomplete measurement settings for entanglement verification in realistic scenarios.

quant-ph↗

arXiv2026

Mirrored Entanglement Witnesses for Multipartite and High-Dimensional Quantum Systems

Entanglement witnesses (EWs) are a versatile tool to detect entangled states and characterize related properties of entanglement in quantum information theory. A witness $W$ corresponds to an observable satisfying $\mathrm{tr}[Wσ_{\mathrm{sep}}]\geq 0$ for all separable states $σ_{\mathrm{sep}}$; entangled states are detected once the inequality is violated. Recently, mirrored EWs have been introduced by showing that there exist non-trivial upper bounds to EWs, \begin{eqnarray} u_W\geq \mathrm{tr}[Wσ_{\mathrm{sep}}]\geq 0. \nonumber \end{eqnarray} An upper bound to a witness $W$ signifies the existence of the other one $M$, called a mirrored EW, such that $W+M = u_W I \otimes I$. The framework of mirrored EWs shows that a single EW can be even more useful, as it can detect a larger set of entangled states by lower and upper bounds. In this work, we develop and investigate mirrored EWs for multipartite qubit states and also for high-dimensional systems, to find the efficiency and effectiveness of mirrored EWs in detecting entangled states. We provide mirrored EWs for $n$-partite GHZ states, graph states such as two-colorable states, and tripartite bound entangled states. We also show that optimal EWs can be reflected with each other. For bipartite systems, we present mirrored EWs for existing optimal EWs and also construct a mirrored pair of optimal EWs in dimension three. Finally, we generalize mirrored EWs such that a pair of EWs can be connected by another EW, i.e., $W+M =K$ is also an EW. Our results enhance the capability of EWs to detect a larger set of entangled states in multipartite and high-dimensional quantum systems.

quant-ph↗

arXiv2024

Machine-learning certification of multipartite entanglement for noisy quantum hardware

Entanglement is a fundamental aspect of quantum physics, both conceptually and for its many applications. Classifying an arbitrary multipartite state as entangled or separable -- a task referred to as the separability problem -- poses a significant challenge, since a state can be entangled with respect to many different of its partitions. We develop a certification pipeline that feeds the statistics of random local measurements into a non-linear dimensionality reduction algorithm, to determine with respect to which partitions a given quantum state is entangled. After training a model on randomly generated quantum states, entangled in different partitions and of varying purity, we verify the accuracy of its predictions on simulated test data, and finally apply it to states prepared on IBM quantum computing hardware.

quant-ph↗

arXiv2021

Detecting Entanglement Generating Circuits in Cloud-Based Quantum Computing

Entanglement, a direct consequence of elementary quantum gates such as controlled-NOT or Toffoli gates, is a key resource that leads to quantum advantages. In this work, we establish the framework of certifying entanglement generation in cloud-based quantum computing services. Namely, we present the construction of quantum circuits that certify entanglement generation in a circuit-based quantum computing model. The framework relaxes the assumption of the so-called qubit allocation, which is the step in a cloud service to relate physical qubits in hardware to a circuit proposed by a user. Consequently, the certification is valid no matter how unsuccessful qubit allocations may be in cloud computing or how untrustful the service may be in qubit allocations. We then demonstrate the certification of entanglement generation on two and three qubits in the IBMQ and IonQ services. Remarkably, entanglement generation is successfully certified in the IonQ service that does not provide a command of qubit allocations. The capabilities of entanglement generation in the circuits of IBMQ and IonQ are also quantified. We envisage that the proposed framework is applied when cloud-based quantum computing services are exploited for practical computation and information tasks, for which our results would find if it is possible to achieve quantum advantages.

quant-ph↗