EPJ Quantum Technology最新文献

In this work we present an alternative methodology to the standard Quantum Accelerated Monte Carlo (QAMC) applied to derivatives pricing. Our pipeline benefits from the combination of a new encoding protocol, referred to as the direct encoding, and an amplitude estimation algorithm, the modified Real Quantum Amplitude Estimation (mRQAE) algorithm. On the one hand, the direct encoding prepares a quantum state which contains the information about the sign of the expected payoff. On the other hand, the mRQAE is able to read all the information contained in the quantum state. Although the procedure we describe is different from the standard one, the main building blocks are almost the same. Thus, all the extensive research that has been performed is still applicable. Moreover, we experimentally compare the performance of the proposed methodology against the standard QAMC employing a quantum emulator and show that we retain the speedups.

In recent years, nitrogen-vacancy centers in diamond have attracted much interest as tools for magnetic field sensing and imaging. Parallel to this progress in science, also in science education, huge advancements are seen, which might even be called an educational quantum revolution, which just has started to emerge.

In this article, we present an experimental setup for optically detectable magnetic resonance (ODMR) in micro-diamonds with nitrogen-vacancy centers (NV centers) which extends the recent work presented in Stegemann et al. (Eur J Phys. 44(3):035402, 2023) in view of better accessibility both from a technical perspective and from an didactical perspective. We improved the mechanical setup, and in particular the output of the measured values, which is now carried out by a microcontroller and is directly accessible to digital devices instead of the need of an oscilloscope. In this way, we increase the accessibility of the experimental setup for learners. Concerning modeling of the theoretical foundations, we discuss the importance of symmetries of the wave function for understanding quantum physics and introduce visualizations for the spin and orbit part of the wave function. Furthermore, we present first empirical data ((N = 53)), indicating possible paths for successful dissemination of the experiments to educators.

The INTENTAS project aims to develop an atomic sensor utilizing entangled Bose-Einstein condensates (BECs) in a microgravity environment. This key achievement is necessary to advance the capability for measurements that benefit from both entanglement-enhanced sensitivities and extended interrogation times. The project addresses significant challenges related to size, weight, and power management (SWaP) specific to the experimental platform at the Einstein-Elevator in Hannover. The design ensures a low-noise environment essential for the creation and detection of entanglement. Additionally, the apparatus features an innovative approach to the all-optical creation of BECs, providing a flexible system for various configurations and meeting the requirements for rapid turnaround times. Successful demonstration of this technology in the Einstein-Elevator will pave the way for a future deployment in space, where its potential applications will unlock high-precision quantum sensing.

The nanoscale fabrication of μm-spaced single-photon emitter arrays is crucial for the development of integrated photonic chips. We report on the fabrication and systematic characterization of germanium-vacancy (GeV) color centers arrays in diamond obtained upon ion implantation at the nanoscale. Ge²⁺ ion implantations at 35 keV and 70 keV energies were carried out using a focused ion beam (FIB) equipped with a liquid metal alloy ion source. The arrays of emitters are subsequently aligned to ø300 nm nanopillar waveguiding structures, fabricated using a combination of electron-beam lithography and plasma etching. The photon collection efficiency and photoluminescence (PL) signal-to-background ratio increased by a factor 8 with respect to the unstructured sample. The photophysical properties of the GeV emitters fabricated by this approach were unaltered with respect to those found in unprocessed diamond. The efficiency of the overall manufacturing process to fabricate individual GeV centers was assessed. Up to 33% of the fabricated nanopillars, depending on ion implantation parameters, were found to contain single emitters.

High relative velocities and large distances in space-based quantum communication with satellites in lower earth orbits can lead to significant Doppler shifts and delays of the signal impairing the achievable performance if uncorrected. We analyze the influence of systematic and stochastic Doppler shift and delay in the specific case of a continuous variable quantum key distribution (CV-QKD) protocol and identify the generalized correlation function, the ambiguity function, as a decisive measure of performance loss. Investigating the generalized correlations as well as private capacity bounds for specific choices of spectral amplitude shape (Gaussian, single- and double-sided Lorentzian), we find that this choice has a significant impact on the robustness of the quantum communication protocol to spectral and temporal synchronization errors. We conclude that optimizing the pulse shape can be a building block in the resilient design of quantum network infrastructure.

As the demand for computing power continues to rise, it is difficult for a single type of computing device or architecture to satisfy the current situation. Diversity and heterogeneity are becoming more and more popular. Seamlessly integrating the realms of high performance computing and quantum computing, and harnessing their collective potential, has emerged as a consensus approach to effectively address the pressing need for increased computing power. In the emerging computing scenario, various different types of computing devices have super-heterogeneous characteristics, and there are significant differences in computational principles, programming models, parallelism, etc. Effectively harnessing these disparate resources and achieving a unified programming paradigm have become urgent imperatives. To address the above problems, this paper introduces QCCP, a taskflow programming model that enables efficient collaborative computing between classical computers and quantum computers. QCCP establishes a unified programming abstraction, shields the super-heterogeneous characteristics of the underlying network and hardware, and supports flexible scheduling for different computational backends. The experimental results indicate that QCCP can support the processing of hybrid classical-quantum applications with diverse program structures. In particular, QCCP reveals its immense potential and superiority in tackling real-world challenges, specifically in the realm of quantum circuit cutting and reconstruction.

The field of Quantum Information Science and Technology (QIST) education presents unique challenges for both students and educators, such as the necessity of understanding abstract properties of quantum systems. To provide a more intuitive understanding of quantum systems, a multitude of qubit representations have been developed in recent years. Given the diversity of the field, a specific representation may be more suitable in one content area of than in another. Consequently, the choice of representation may vary considerably depending on the course orientation. However, no exhaustive analysis has been conducted into the differences between the representation of single- and multi-qubit systems in higher education QIST courses. Furthermore, the factors which influence the selection of a suitable representation remain open. To close this gap, we conducted an online survey with 25 educators at different German and Austrian universities on their use of representations in QIST-related courses. The results confirm the pivotal role of mathematical formalism in QIST education regardless of the specific course characteristics but also reveal an untapped potential for enhancing student learning through the intentional and comprehensive use of multiple external representations (MERs), especially in the case of multi-qubit systems. The findings are discussed within the context of the field of QIST and current insights into learning with MERs.

The violation of a Bell inequality implies the existence of nonlocality, making device-independent randomness certification possible. This paper derives a tight upper bound for the maximal quantum violation of Gisin’s elegant Bell inequality (EBI) for arbitrary two-qubit states, along with the constraints required to achieve this bound. This method provides the necessary and sufficient conditions for violating the EBI for several quantum states, including pure two-qubit states and the Werner states. The lower bound of certifiable global randomness is analyzed based on the tight upper bound of the EBI for pure two-qubit states, with a comparison to the Clauser-Horne-Shimony-Holt (CHSH) inequality. The relationship between the noise level and the lower bound of certifiable global randomness with respect to the Werner states is also explored, and the comparisons with both the CHSH inequality and the chained inequality are given. The results indicate that when the state approaches a maximally entangled state within specific quantified ranges, the EBI demonstrates advantages over both the CHSH inequality and the chained inequality, providing theoretical guidance for experimental device-independent quantum random number generation.

Characterization and exploitation of multiple channels between the transmitter and the receiver in multiple-input multiple-output (MIMO) communications brought a paradigm shift in classical communication systems. The techniques developed around MIMO communication systems not only brought unprecedented advancements in communication rates but also substantially improved the reliability of communication, measured by low error rates. We develop a framework for MIMO quantum communications with discrete-variable quantum systems. We propose a general model of MIMO quantum channels incorporating noise, losses, and crosstalk among multiple channels. We leverage the approximate quantum cloning to transmit imperfect clones of the input state over this channel setup. We demonstrate that transmitting multiple imperfect clones achieves better communication fidelity as compared to transmitting a single perfect copy of the state due to the diversity of the MIMO setup. We also demonstrate a practical tradeoff between fidelity and rate of communication and call it quantum diversity multiplexing tradeoff (DMT) due to its similarity with the well-known DMT in classical MIMO setups.

In quantum cryptography, secret communications are delivered through a quantum channel. One of the most important breakthroughs in quantum cryptography has been the quantum key distribution (QKD). This process enables two distant parties to share secure communications based on physical laws. However, eavesdroppers can still interrupt the communication. To overcome this, we propose a different way to detect the presence of Eve through the polynomial interpolation technique. This technique also allows us for key verification. This approach prevents the receiver as well as the intruder from discovering the sender’s fundamental basis. To fully utilize IBM quantum computers’ quantum computing capabilities, this paper attempts to show % error against alpha (strength of eavesdropping) and the impact of noise on the success probability of the desired key bits. Furthermore, the success probability under depolarizing noise is explained for different qubit counts. In the enhanced QKD protocol, using polynomial interpolation for reconciliation shows a 50% probability of successful key generation. This is even when the noise is increased to the maximum capacity.