Qubits Research Articles

A Review of Significant Challenges with Quantum Communication and Computing

Recent times have witnessed tremendous competition towards quantum optics in business as well as academia, motivated by rapid growth in quantum computing. Overall scalability of quant present invention relates generally has exceeded several orders of magnitude, whereas ubiquitous quantum computers has accommodated as many as hundreds of quantum bits (i.e., thousands of qubits). Robust machines are still being created. Therefore, ethnicity has motivated an immense amount of research papers and reports. For all those people who read would really like to learn further the concepts of quant communication and computing from the machine learning perspective, this article provides an introduction. It begins with such an informative approach until continuing well over key turning points and most recent developments in quantum computing. These core features of such a virtual network are broken down into four significant issues in this paper, each of which has been closely investigated. A, B, C, and D are quantum mechanics, networking, security, and algorithms, accordingly. The article wraps up with the major challenges, the significant research areas, as well as the latest developments.

Hunting for Majoranas.

Over the past decade, there have been considerable efforts to observe non-abelian quasiparticles in novel quantum materials and devices. These efforts are motivated by the goals of demonstrating quantum statistics of quasiparticles beyond those of fermions and bosons and of establishing the underlying science for the creation of topologically protected quantum bits. In this Review, we focus on efforts to create topological superconducting phases that host Majorana zero modes. We consider the lessons learned from existing experimental efforts, which are motivating both improvements to present platforms and the exploration of new approaches. Although the experimental detection of non-abelian quasiparticles remains challenging, the knowledge gained thus far and the opportunities ahead offer high potential for discovery and advances in this exciting area of quantum physics.

Quantum Key Distribution Using a Quantum Emitter in Hexagonal Boron Nitride

AbstractQuantum key distribution (QKD) is considered the most immediate application to be widely implemented among a variety of potential quantum technologies. QKD enables sharing secret keys between distant users by using photons as information carriers. An ongoing endeavor is to implement these protocols in practice in a robust, and compact manner so as to be efficiently deployable in a range of real‐world scenarios. Single photon sources (SPS) in solid‐state materials are prime candidates in this respect. This article demonstrates a room temperature, discrete‐variable quantum key distribution system using a bright single photon source in hexagonal‐boron nitride, operating in free‐space. Employing an easily interchangeable photon source system, keys with one million bits length, and a secret key of approximately 70000 bits, at a quantum bit error rate of 6%, with ε‐security of 10−10 are generated. This study demonstrates the first proof of concept finite‐key BB84 QKD system realized with hBN defects.

Influence of random telegraph noise on quantum bit gate operation

We consider the problem of analyzing spin-flip qubit gate operation in the presence of Random Telegraph Noise (RTN). Our compressive approach is the following. By using the Feynman disentangling operators method, we calculate the spin-flip probability of qubit driven by different kinds of composite pulses, e.g., Constant pulse (C-pulse), Quantum Well pulse (QW-pulse), and Barrier Potential pulse (BP-pulse) in the presence of RTN. When composite pulses and RTN act in the x-direction and z-direction respectively, we calculate the optimal time to achieve perfect spin-flip probability of qubit. We report that the highest fidelity of spin-flip qubit can be achieved by using C-pulse, followed by BP-pulse and QW-pulse. For a more general case, we have tested several pulse sequences for achieving high fidelity quantum gates, where we use the pulses acting in different directions. From the calculations, we find that high fidelity of qubit gate operation in the presence of RTN is achieved when QW-pulse, BP-pulse, and C-pulse act in the x-direction, y-direction, and z-direction, respectively. We extend our investigations for multiple QW and BP pulses while choosing the C-pulse amplitude constant in the presence of RTN. The results of calculation show that 98.5% fidelity can be achieved throughout the course of RTN that may be beneficial for quantum error correction.

Dissipative dynamics in quantum key distribution

Using the IBM Quantum Experience platform, we simulate the dissipative dynamics in the BB84 quantum key distribution protocol. We employ the Jaynes–Cummings model to simulate the attenuation in an optical fiber during the information transmission process and calculate the quantum bit error rate (QBER). The results of QBER as a function of the distance give a satisfactory agreement with experimental data when the system is in a Markovian regime.

Implementation of Combinational and Sequential Logic Circuits using Quantum Computing

Quantum computing is an area of computer science that uses the principles of quantum theory. Quantum computing is a booming field and could lead significant advances in various fields, from chemistry to material science to nuclear physics and machine learning. Quantum computing uses quantum bits as a fundamental building block of computations. The power of quantum bits is their ability to scale exponentially, which makes complex computations faster and efficient. The objective of this paper is to design Flip Flops and combinational logic circuits using quantum computing. Flip Flops and combinational circuits assist in complex computations with reduced delay, and high efficiency when designed using quantum computing. The flip flops and adders can henceforth be used in several applications.

Multipartite Dense Coding in Social Internet of Things

The world today is interconnected. As we live in the contemporary era, we will undoubtedly feel the importance of information interaction in all aspects. This kind of information interaction needs to be carried out or mediated. Quantum communication is a new way of information interaction that has been pushed to the forefront in the past decade. It not only has the low cost of traditional radio communication but also has the characteristics of long relay distance of optical communication system. Compared with these characteristics, the most important thing is that it has super high confidentiality. This is the most critical point in the information age. Dense coding is an important application of quantum information. It reflects the difference between quantum bits and classical bits in transmission, providing a reliable theoretical basis for improving the effectiveness of remote communication in the future. We discuss two kinds of extensions of the original dense coding. They respectively work for high-dimension and multipartite situations. We give the laws of the two attachments. In the high-dimensional system, we use the Bell state as the target state of any quantum state and realize the one-to-one correspondence between the entangled state and the Bell state. In multipartite space, we can find that the transformation results can form a dimensional space, and the quantum states obtained are one-to-one, corresponding to the classical bit states. In the multipartite system, we can get the transmitted information more efficiently and accurately by limiting data processing by partial senders. At the same time, this restriction will not reduce the amount of information transmitted initially. Therefore, this limited transformation can improve quantum computing power without damaging quantum states.

Design Space Exploration for Efficient Quantum Most-Significant Digit-First Arithmetic

Quantum computing has been considered as an emerging approach in addressing problems which are not easily solvable using classical computers. In parallel to the physical implementation of quantum processors, quantum algorithms have been actively developed for real-life applications to show quantum advantages, many of which benefit from quantum arithmetic algorithms and their efficient implementations. As one of the most important operations, quantum addition has been adopted in Shor's algorithm and quantum linear algebra algorithms. Although various least-significant digit-first quantum adders have been introduced in previous work, interest in investigating the efficient implementation of most-significant digit-first addition is growing. In this work, we propose a novel design method for most-significant digit-first addition with several quantum circuit optimisations to reduce the number of quantum bits ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i.e.</i> qubits), quantum gates, and circuit depth. An open-source library of different arithmetic operators based on our proposed method is presented, where all circuits are implemented on IBM Qiskit SDK. Extensive experiments demonstrate that our proposed design, together with the optimisation techniques, reduces T-depth by up-to 4.0×, T-count by 3.5×, and qubit consumption by 1.2×.

Integrated photonic platforms for quantum technology: a review

Quantum information processing has conceptually changed the way we process and transmit information. Our understanding of quantum physics, which explains the seemingly strange behavior of matter at the microscopic scales, has matured to the extent that we can now explore technologies based on the phenomenon. One such exciting application of quantum physics with far-reaching consequences is quantum computing. Quantum computing, which uses quantum bits (qubits) for information processing, has changed the way we process and transmit information in a fundamental way. Experiments suggest that the most successful candidates for realizing qubits are photons. Therefore, integrated photonic platforms play a crucial role in harnessing the potential of quantum technology. This paper surveys the various photonic platforms based on different materials for quantum information processing. The future of this technology depends on the successful materials that can be used to universally realize quantum devices, similar to silicon, which shaped the industry toward the end of the last century. While it would be hazardous to make definitive predictions about the quantum revolution, our overview of the current status of research on the various platforms based on the materials used could shed light on how the future of quantum computing could unfold.

RSA Prime Factorization on IBM Qiskit

The advancement of quantum computing in recent years poses severe threats to the RSA public-key cryptosystem. The RSA cryptosystem fundamentally relies its security on the computational hardness of number theory problems: prime factorization (integer factoring). Shor’s quantum factoring algorithm could theoretically answer the computational problem in polynomial time. This paper contributes to the experiment and demonstration of Shor’s quantum factoring algorithm for RSA prime factorization using IBM Qiskit. The performance of the quantum program is evaluated based on user time and the success probability. The results show that a more significant public modulus N in the RSA public key improves factorization’s computational hardness, requiring more quantum bits to solve. A further enhancement on implementing Shor’s oracle function is essential in increasing success probability and reducing the number of shots required.

Quantum healthcare computing using precision based granular approach

Previously, doctors interpreted diseases and their outcomes according to their experience in diagnosis. However, with the rapid increase in technology and population, the task of examining the patient becomes cumbersome and sometimes human efforts produce inconsistent results. Several research is being done for healthcare in terms of improving visualization and accuracy by using machine learning models. The current research targets to explore quantum computing as a different way of processing information compared to classical computer systems such as the use of quantum bits (qubits) along with superposition and entanglement for extending the computation capabilities at an unprecedented level of thinking in the healthcare domain. Quantum computing systems provide exponential benefits in terms of high-speed processing, faster and easier diagnostic assistance, unimaginable reduction in processing throughput, and many more. An extensive comparative analysis of existing approaches has been made which benchmarks the need for quantum healthcare computing. The objective of this work is to interpret whether Quantum computers prove to be more trusted when it comes to patient diagnosis, and faster analysis leading to cost optimization. In order to accelerate patient diagnosis, different approaches have been presented. The authors have proposed a precision-based granular approach for patient diagnosis that incorporates diagnosing the disease with enhanced precision and granularity. It involves reporting symptoms by the patient, encountering by healthcare expert on multiple factors, precise examination, granular health status (understanding past and present medical history), followed by a precise intervention by understanding biomolecular simulations. The algorithm has been presented to describe the flow process for patient diagnosis modeling using quantum computing. It involves qubits initialization, pairing the values, assigning probabilistic values, cross-validation, and quantum circuit formation. Precision-based granular approach has been implemented for a scenario (consisting of medical parameters such as oxygen and heart rate level, with the functionality of diagnosing oxygen level and heart range which lies as either normal or not normal (high/low)). Precision-based granular approach deals specifically with the individual ‘biomolecular simulation by understanding variations in the individual body whereas the umbrella-based approach does not deal with specifically to individual mechanisms. Granular level of encounter is not possible in umbrella-based treatment. Python Jupyter notebook and IBM Composer tool is used for the implementation of results. Bloch sphere and computational state graph are obtained as an output for better visualization and understanding. Falcon r5.11H processor is used with the version of 1.0.24 of IBM Composer to simulate the experiment. The methodology using precision based granular approach provides timely encounter of disease along with umbrella diagnosis and precise treatment. The time is taken and frequency of qubits have been presented with promising results. The diagnosis process and optimizing cost efficiency can aid in an early detection of the disease.

High-speed integrated QKD system

Quantum key distribution (QKD) is nowadays a well-established method for generating secret keys at a distance in an information-theoretically secure way, as the secrecy of QKD relies on the laws of quantum physics and not on computational complexity. In order to industrialize QKD, low-cost, mass-manufactured, and practical QKD setups are required. Hence, photonic and electronic integration of the sender’s and receiver’s respective components is currently in the spotlight. Here we present a high-speed (2.5 GHz) integrated QKD setup featuring a transmitter chip in silicon photonics allowing for high-speed modulation and accurate state preparation, as well as a polarization-independent low-loss receiver chip in aluminum borosilicate glass fabricated by the femtosecond laser micromachining technique. Our system achieves raw bit error rates, quantum bit error rates, and secret key rates equivalent to a much more complex state-of-the-art setup based on discrete components [ Boaron A. et al. , Phys. Rev. Lett. 121, 190502 (2018)].

Epitaxy of Group-IV Semiconductors for Quantum Electronics

We are growing at CEA (i) high purity 28Si layers and (ii) c-Ge/SiGe heterostructures for electron and hole spin quantum bits. We describe here strategies usable for the fabrication of 28SOI substrates, with a focus on 28SiH4 consumption minimization, as such a gas is very expensive and hard to come by. We also focus on the properties of Si0.26Ge0.74 and Si0.21Ge0.79 Virtual Substrates (VS) grown at 850°C, 20 Torr and a forward Ge ramping-up on Si(001) substrates. After some chemical polishing (to remove the surface cross-hatch), those VS are used as templates for the 500°C, 100 Torr growth of SiGe/c-Ge/SiGe 2D Hole Gas Gas (2DHG) stacks. Those c-Ge layers are, in X-Ray Diffraction, fully compressively strained on the relaxed SiGe VS underneath and of high crystalline quality. Some slight undulations are evidenced at c-Ge / SiGe cap interfaces, hinting at elastic strain relaxation, however. Magnetotransport measurements in Hall-bar devices were performed at 4.2 K to assess the electrical properties of the 2DHG in those SiGe/c-Ge heterostructures. At low magnetic field, a hole mobility of 1.2 x 105 cm2 V-1 s-1 was obtained for a hole density of n2DHG = 3.7x1011 cm-2 in a 16 nm thick c-Ge/55 nm thick Si0.21Ge0.79 cap sample.

Hybrid High-Dimensional Quantum Key Distribution for a Composable Quantum Network

High-dimensional quantum key distribution (HD-QKD) possesses a higher noise-tolerance ability and secure key rate. In the work presented here, by developing a mapping method for multiple degrees of freedom (DOFs), we propose and implement a HD-QKD system with a quantum bit error rate as low as 0.57%. Our HD-QKD system can stably achieve high secure key rates and is composable, allowing one to build HD quantum networks compatible with multiple DOFs. The results indicate that the proposed scheme could bridge HD and two-dimensional terminals encoded in different DOFs and could support large-scale deployment of quantum networks with high performance. Our work significantly enhances the performance of HD-QKD and strengthens the practical applications of large-scale quantum networks in a hybrid way.

Quantum Bit Commitment Without Quantum Memory

Abstract Commitment scheme is a fundamental cryptographic primitive that serve as building blocks for many other two-party protocols. In this paper, we propose a novel quantum bit commitment scheme, which is secure and does not require quantum memory. Our scheme processes the quantum information using coherent states and unambiguous state discrimination (USD) measurements, which can be experimentally realized by linear optics and photon detectors. We ensure the unconditionally hiding and binding property by preventing both Alice and Bob from obtaining complete information about the commitment in committing stage, and eliminate the requirement for quantum memory by performing USD measurements and phase shifts immediately after receiving the coherent states.

QiCells: A Modular RFSoC-based Approach to Interface Superconducting Quantum Bits

Quantum computers will be a revolutionary extension of the heterogeneous computing world. They consist of many quantum bits (qubits) and require a careful design of the interface between the classical computer architecture and the quantum processor. For example, even single nanosecond variations of the interaction may have an influence on the quantum state. Designing a tailored interface electronics is therefore a major challenge, both in terms of signal integrity with respect to single channels, as well as the scaling of the signal count. We developed such an interface electronics, an RFSoC-based qubit control system called QiController. In this article, we present the modular FPGA firmware design of our system. It features so-called digital unit cells, or QiCells. Each cell contains all the logic necessary to interact with a single superconducting qubit, including a custom-built RISC-V-based sequencer. Synchronization and data exchange between the cells is facilitated using a special star-point structure. Versatile routing and frequency-division multiplexing of generated signals between QiCells and converters are also supported. High-level programmability is provided using a custom Python-based description language and an associated compiler. We furthermore provide the resource utilization of our design and demonstrate its correct operation using an actual superconducting five-qubit chip.

Investigation of oxygen-vacancy complexes in diamond by means of ab initio calculations

Point defects in diamond may act as quantum bits. Recently, oxygen-vacancy related defects have been proposed to the origin of the so-called ST1 color center in diamond that can realize a long-living solid-state quantum memory. Motivated by this proposal we systematically investigate oxygen-vacancy complexes in diamond by means of first principles density functional theory calculations. We find that all the considered oxygen-vacancy defects have a high-spin ground state in their neutral charge state, which disregards them as an origin for the ST1 color center. We identify a high-spin metastable oxygen-vacancy complex and characterize their magneto-optical properties for identification in future experiments.

Quantum bit threads

We give a bit thread prescription that is equivalent to the quantum extremal surface prescription for holographic entanglement entropy. Our proposal is inspired by considerations of bit threads in doubly holographic models, and equivalence is established by proving a generalisation of the Riemannian max-flow min-cut theorem. We explore our proposal’s properties and discuss ways in which islands and spacetime are emergent phenomena from the quantum bit thread perspective.

Multilayered logical qubits and synthesized quantum bits

Quantum error correction is likely to be key in obtaining near term quantum advantage. We propose a novel method for providing multiple logical qubits in the correction of quantum errors using classical computers. The core idea of our work is built upon two main pillars: dividing the Hilbert space into reduced Hilbert spaces with individual logical qubits and synthesizing the reduced Hilbert spaces through a mathematical collaborating between classical bits and logical quantum states. We demonstrate that our method supports at least 20 logical qubits in a surface code with a code distance of 3. Furthermore, we generate entangled states of multiple logical qubits from lattice surgery-based surface codes using only physical qubit operations. This approach enables classical computers to support a larger number of logical qubits using less memory and perform faster simulations.

Quantum identity authentication based on the extension of quantum rotation

In this work, we propose a bit-oriented QIA protocol based on special properties of quantum rotation and the public key cryptographic framework. The proposed protocol exhibited good resistance to both forward search and measure-resend attacks, whereby its security performance was directly related to the length of the authentication code. From our analysis, it was demonstrated that the protocol has good performance, in terms of quantum bit efficiency. In addition, the protocol is well-expandable. The developed protocol is resource-efficient and can be also applied in quantum computing networks.