Auxiliary Bits Research Articles

Improved Quantum Rebound Attacks on Double Block Length Hashing with Round-Reduced AES-256 and ARIA-256

At EUROCRYPT 2020, Hosoyamada and Sasaki proposed the first dedicated quantum collision attacks on hash functions. Their proposal presented a quantum adaptation of the rebound attack and revealed that differential trails, which have too low probability for use in classical settings, might be exploitable in quantum settings. After their work, subsequent research has actively delved into analyzing the security of hash functions in the quantum setting.In this paper, we revisit the quantum rebound attacks on the double block hash function Hirose instantiated with 10-round AES-256 (HCF-AES-256) and 7-round ARIA-256 (HCF-ARIA-256) proposed by Chauhan et al. and Baek et al., respectively. Initially, we identify the flaws in their work and reevaluate the complexity of the attacks. We reveal that the flaws stem from not considering the issue that the S-box differential equation has one solution on average. Earlier research addressed this problem by adding auxiliary bits to the search space. If this method is used to correct the flaws, the resulting time complexities are 217.36 and 220.94 times higher than their proposals. Consequently, in some settings, their attacks become less efficient than generic attacks.Subsequently, we propose improved quantum rebound attacks using nested quantum amplitude amplification and quantum state preparation. Our improved attack efficiently pre-filters the search space, leading to a reduction in overall time complexity. We first classically reduce the search space and employ quantum state preparation to generate a superposition state over the pre-filtered search space. We then use nested quantum amplitude amplification to further reduce the search space quantumly. As a result, we achieve a reduction in the time complexity of the quantum rebound attacks on HCF-AES-256 and HCF-ARIA-256 by factors of 211.2 and 219.5, respectively, making the attacks more efficient than generic attacks again.

Research progress of integrated optical quantum computing

<sec>Quantum computing, based on the inherent superposition and entanglement properties of quantum states, can break through the limits of classical computing power. However, under the present technical conditions, the number of qubits that can be manipulated is still limited. In addition, the preparation of high-precision quantum gates and additional quantum error correction systems requires more auxiliary bits, which leads to extra cost. Therefore, it seems to be a long-term goal to realize a universal fault-tolerant quantum computer.</sec><sec>The development of analog quantum computing is a transition path that can be used to simulate many-body physics problems. Quantum walk, as the quantum counterpart of classical random walks, is a research hotspot in analog quantum computing. Owing to the unique quantum superposition characteristics, quantum walk exhibits the ballistic transport properties of outward diffusion, so quantum walk provides acceleration in computing power for various algorithms. Based on quantum walk, different computing models are derived to deal with practical physical problems in different fields, such as biology, physics, economics, and computer science.</sec><sec>A large number of technical routes are devoted to the experiments on realizing quantum walk, including optical fiber networks, superconducting systems, nuclear magnetic resonance systems, and trapped ion atom systems. Among these routes, photons are considered as the reliable information carriers in the experiments on quantum walking due to their controllability, long coherence time. and fast speed.</sec><sec>Therefore, in this review, we focus on different quantum walk theories and experimental implementations in optical versions, such as traditional optical platforms, optical fiber platforms, and integrated optical quantum platform. In recent years, the rapid development of integrated optical quantum platforms has driven the experiments on quantum walk to move towards the stage of integration and miniaturization, and at the same time, the experimental scale and the number of qubits have gradually increased.</sec><sec>To this end, we summarize the technological progress of integrated optical quantum computing, including various integrated optical quantum experimental platforms and their applications. Secondly, we specifically discuss the experiment on quantum walk and practical applications based on integrated optical quantum platforms. Finally, we briefly describe other quantum algorithms and corresponding experimental implementations.</sec><sec>These quantum computing schemes provide computational speedups for specific physical problems. In the future, with the further development of integrated optical quantum technology, along with the increase in the number of controllable qubits and the realization of the supporting quantum error correction system, a larger-scale many-body physical system can be constructed to further expand these algorithms and move towards the field of optical quantum computing, a new stage.</sec>

Sustainable disturbance crosstalk mitigation in deeply scaled phase-change memory

While Phase Change Memory (PCM) is gaining popularity in next generation systems compared to conventional DRAM and Flash, write disturbance due to crosstalk remains a significant challenge to PCM performance and reliability. To address this concern we propose a multi-tiered compression (MTC) technique combined with novel encoding that can decrease the probability of write disturbance. MTC compresses a high proportion (>94%) of cachelines by a small predictable amount (e.g., 40- or 56-bits of a 512-bit block) while maintaining data similarity vital for optimizing PCM writes. By detecting data patterns prone to crosstalk, we use encoding, correction pointers, and a hybrid approach to reduce the instances of write disturbance. We use MTC reclaimed bits to store the encoding. Thus, our approach requires only five additional auxiliary bits per 512-bit cacheline, minimizing the embodied energy (fabrication) overhead to mitigate write disturbance. Additionally, through a multi-objective optimization, dramatic endurance improvements are possible while maintaining nearly all write disturbance improvement.Our technique improves performance, endurance and write energy by 47%, 42% and 36% versus the state-of-the-art with nominal (circa 1%) increases to embodied energy. When considering the full life-cycle impact, the additional area of our MTC with encoding approach is mitigated by the use-phase benefits within 60 days for a high performance system and in less than four years of use for a desktop system. In nearly all studied scenarios, the improved lifetime provided by our MTC and encoding approach easily recoups the required additional upfront manufacturing energy.

Novel multi-bit quantum comparators and their application in image binarization

Quantum image processing has attracted much attention since it offers a potential solution to efficiently calculate some hard problems much faster than classical image processing. In particular, it is a basic operation to change each image pixel into black or white, named as a binary image. Here we present novel multi-bit quantum comparators to realize quantum image binarization. These comparators compare two quantum logic states and identify which of them is the largest. We analyze the superior performance of our proposed comparators in terms of quantum cost, quantum delay and auxiliary bits compared with the existing comparators. Furthermore, our quantum image binarization exploits the advantages of our proposed multi-bit comparators to change the values of image pixels into 0 or 255.

Data Block Partitioning Methods to Mitigate Stuck-At Faults in Limited Endurance Memories

Deep scaling in conjunction with increased process variation has resulted in increasingly faulty memories. Emerging memories, particularly phase-change and resistive memories, can experience stuck-at faults due to limited endurance. Partition and flip (PAF) schemes partition data into blocks and invert these blocks as needed to ensure data that is written matches the stuck-at cells. In this paper, we propose two novel correction schemes that substantially enhance the fault-tolerance capabilities of existing PAF techniques. First, dynamic partitioning increases the number of possible configurations with equivalent auxiliary bits. At high fixed error rates, the increase in configurations results in improved write error rates for flip-N-write and Aegis partitioning by 7%–72% and 5– $53\times $ , respectively. Our second novel partitioning method, relaxed partitioning, dramatically and effectively increases the partitioning search space by specifying minimally overlapping configurations. Through Monte Carlo simulations, data-aware dynamic partitioning tolerates 25% and 27% more faults over its lifetime than Aegis with 36 and 43 auxiliary bits per 512-bit data block, respectively, while relaxed partitioning achieves an extra 15% and 24% additional improvement while requiring two fewer overhead bits per data block.

Yielding optimized dependability assurance through bit inversion

Phase change memory (PCM) is a promising alternative to conventional DRAM main memories, due to its read performance, density, and nonvolatility and resulting low static energy. Unfortunately, reliability is still a significant challenge as limited write endurance, exacerbated by process variation, leads to increasing numbers of stuck-at faults over the memory's lifetime. This includes a significant number of stuck-at faults that appear early in the memory's service. Error-correcting Pointers (ECP) is a popular proposal to mitigate stuck-at faults in PCM by recording the addresses and the values of faulty bits in order to extend the lifetime of the memory. We propose a method to extend the effectiveness of ECP coverage called Yoda, which utilizes a small number of additional encoding bits in order to dramatically improve the effectiveness and fault correction capability of ECP. By adding one additional bit to ECP which corrects f faults, Yoda can correct 2f +1 faults. Further improvements are possible introducing small numbers additional bits. Our simulation results demonstrate that Yoda has a 3.0× improvement in fault coverage compared to a fault-aware ECP with a similar overhead, while also providing a 2.5–3.0× improvement over state-of-the-art schemes with comparable complexity. Furthermore, Yoda provides a method to protect the auxiliary bits, also with a small overhead. By adding one auxiliary bit to protect the auxiliary bits, Yoda can achieve extra improvement.

An Efficient Design of Reversible Multi-Bit Quantum Comparator Via Only a Single Ancillary Bit

Quantum computing has emerged as one of the most promising technology due to its powerful computing capability. And quantum basic circuits like quantum comparator, quantum adder etc, are the foundation to realize quantum computing. In this paper, we present an efficient design to realize the comparison of two n-bit quantum logic states via only a single ancillary bit. Our proposed comparator compares two n-bit quantum logic states and identifies which of them is the largest, which of them is the smallest, and which of them is equal in linear quantum depth. Moreover, we analyze the superior performance of our proposed comparator in terms of auxiliary bits compared with the existing quantum logic comparators.

Practical Dirty Paper Coding With Sum Codes

In this paper, we present a practical method to construct dirty paper coding (DPC) schemes using sum codes. Unlike the commonly used approach to DPC where the coding scheme involves concatenation of a channel code and a quantization code, the proposed method embodies a unified approach that emulates the binning method used in the proof of the DPC result. Auxiliary bits are used to create the desired number of code vectors in each bin. Sum codes are obtained when information sequences augmented with auxiliary bits are encoded using linear block codes. Sum-code-based DPC schemes can be implemented using any linear block code, and entail a relatively small increase in decoder complexity when compared to standard communication schemes. They can also lead to significant reduction in transmit power in comparison to standard schemes.

Preparation of three-qubit decoherence-free state via quantum Zeno dynamics

We propose two schemes to generate three-qubit decoherence-free state for atoms trapped in a cavity via quantum Zeno dynamics. The influence of various decoherence processes such as spontaneous emission and photon loss on the fidelity of the entangled state is investigated. Numerical results show that the schemes are robust against the cavity decay since the evolution of the system is restricted to a subspace with null-excitation cavity fields. Moreover, no measurement, post selection and auxiliary bits are needed during the whole process.

Algorithmic cooling and scalable NMR quantum computers.

We present here algorithmic cooling (via polarization heat bath)-a powerful method for obtaining a large number of highly polarized spins in liquid nuclear-spin systems at finite temperature. Given that spin-half states represent (quantum) bits, algorithmic cooling cleans dirty bits beyond the Shannon's bound on data compression, by using a set of rapidly thermal-relaxing bits. Such auxiliary bits could be implemented by using spins that rapidly get into thermal equilibrium with the environment, e.g., electron spins. Interestingly, the interaction with the environment, usually a most undesired interaction, is used here to our benefit, allowing a cooling mechanism. Cooling spins to a very low temperature without cooling the environment could lead to a breakthrough in NMR experiments, and our "spin-refrigerating" method suggests that this is possible. The scaling of NMR ensemble computers is currently one of the main obstacles to building larger-scale quantum computing devices, and our spin-refrigerating method suggests that this problem can be resolved.