Quantum supremacy in many applications using well-known quantum algorithms rely on availability of data in quantum format. Quantum Random Access Memory (QRAM), an equivalent of classical Random Access Memory (RAM), fulfills this requirement. However, the existing QRAM proposals either require qutrit technology and/or incur access challenges. We propose an approximate Parametric Quantum Circuit (PQC) based QRAM which takes address lines as input and gives out the corresponding data in these address lines as the output. We present two applications of the proposed PQC-based QRAM namely, storage of binary data and storage of machine learning (ML) dataset for classification.
Quantum supremacy in many applications using well-known quantum algorithms rely on availability of data in quantum format. Quantum Random Access Memory (QRAM), an equivalent of classical Random Access Memory (RAM), fulfills this requirement. However, the existing QRAM proposals either require qutrit technology and/or incur access challenges. We propose an approximate Parametric Quantum Circuit (PQC) based QRAM which takes address lines as input and gives out the corresponding data in these address lines as the output. We present two applications of the proposed PQC-based QRAM namely, storage of binary data and storage of machine learning (ML) dataset for classification.
Quantum Machine Learning (QML) is a new domain of Machine Learning (ML) and Quantum Computing (QC) that uses a trainable Variational Quantum Circuit (VQC) to solve various learning problems. Classical data is transformed to the quantum Hilbert space using an embedding scheme and the VQC performs quantum operations on this transformed quantum data using parametric quantum gates. In this work, we present a new embedding scheme using Quantum Random Access Memory (QRAM) that takes address as input, and gives data as the output similar to a classical Random Access Memory (RAM). We propose a basic circuit-based QRAM architecture and its application in, (a) storage for ML usage and, (b) storage of binary data. For ML, we store images of digits dataset into the QRAM and perform binary classification using a Quantum Neural Network (QNN). We observe that QNN driven by the proposed QRAM converges faster (at6thepoch) with 100% classification accuracy compared to QNN with normal embedding and classical Fully Connected Neural Network (FCNN) setups which converge with same accuracy at around10thand15thepochs, respectively. We obtain≈63%classification accuracy on real hardware from IBM. For storage of binary data, we measure Hamming Distance (HD) and percentage correct predictions for quality evaluation of the proposed QRAM. We observe that the HD and percentage correct predictions worsens as the number of address lines increases. We propose two techniques to improve the QRAM accuracy namely, (i) clustering of raw data and allocating one QRAM per cluster and, (ii) bit splitting to divide wider data into smaller chunks and allocating one QRAM per split. Clustering provides best results by improving the HD for 9-address QRAM by≈1.95Xthan pure QRAM and≈1.74Ximprovement compared to bit-split (which provides≈1.11Ximprovement than pure QRAM).
Quantum Random Access Memory (QRAM) has the potential to revolutionize the area of quantum computing. QRAM uses quantum computing principles to store and modify quantum or classical data efficiently, greatly accelerating a wide range of computer processes. Despite its importance, there is a lack of comprehensive surveys that cover the entire spectrum of QRAM architectures. We fill this gap by providing a comprehensive review of QRAM, emphasizing its significance and viability in existing noisy quantum computers. By drawing comparisons with conventional RAM for ease of understanding, this survey clarifies the fundamental ideas and actions of QRAM. QRAM provides an exponential time advantage compared to its classical counterpart by reading and writing all data at once, which is achieved owing to storage of data in a superposition of states. Overall, we compare six different QRAM technologies in terms of their structure and workings, circuit width and depth, unique qualities, practical implementation, and drawbacks. In general, with the exception of trainable machine learning-based QRAMs, we observe that QRAM has exponential depth/width requirements in terms of the number of qubits/qudits and that most QRAM implementations are practical for superconducting and trapped-ion qubit systems.
The burgeoning field of machine learning (ML) is increasingly reliant on massive datasets for training complex models, particularly deep neural networks. However, the retrieval of data from conventional memory systems represents a significant bottleneck, limiting the scalability and efficiency of ML algorithms. This research proposes a Quantum Random Access Memory (QRAM) architecture designed to overcome this limitation by leveraging quantum mechanical principles. The core concept involves encoding data into qubits and utilizing quantum random access to achieve near-instantaneous data retrieval. This paper details a novel QRAM architecture, focusing on qubit arrangement, control mechanisms, and strategies for minimizing decoherence – a primary challenge in quantum computing. The theoretical framework explores the potential acceleration achievable through QRAM in deep neural network training, with the primary goal of dramatically reducing training times. We present a detailed mathematical model outlining the data encoding process, quantum access protocols, and the expected performance gains. The architecture incorporates error mitigation techniques and discusses the scalability of the design for increasingly complex datasets. The research highlights the transformative potential of QRAM in accelerating ML, addressing a fundamental constraint within the current landscape of computational learning.
Using quantum algorithms to carry out ML tasks is what is known as Quantum Machine Learning (QML) and the methods developed within this field have the potential to outperform their classical counterparts in solving certain learning problems. The development of the field is partly dependent on that of a functional quantum random access memory (QRAM), called for by some of the algorithms devised. Such a device would store data in a superposition and could then be queried when algorithms require it, similarly to its classical counterpart, allowing for efficient data access. Taking an axiomatic approach to QRAM, this thesis provides the main considerations, assumptions and results regarding QRAM and yields a QRAM handbook and comprehensive introduction to the literature pertaining to it.
Owing to the significant progress in manufacturing desktop quantum computers, the quest to achieve efficient quantum random access memory (QRAM) became inevitable. In this paper, we propose a novel efficient random access memory for quantum computers. The proposed QRAM has a fixed structure and can be used efficiently to store both known and unknown classical/quantum data. The storage capacity of the proposed QRAM is more efficient than that of the classical RAMs and can be used to store both classical and quantum information. Furthermore, the proposed model can access an arbitrary location in O(1) compared with other state-of-the-art models.
A random access memory, or RAM, is a device that, when interrogated, returns the content of a memory location in a memory array. A quantum RAM, or qRAM, allows one to access superpositions of memory sites, which may contain either quantum or classical information. RAMs and qRAMs with n-bit addresses can access 2n memory sites. Any design for a RAM or qRAM then requires O(2n) two-bit logic gates. At first sight this requirement might seem to make large scale quantum versions of such devices impractical, due to the difficulty of constructing and operating coherent devices with large numbers of quantum logic gates. Here we analyze two different RAM architectures (the conventional fanout and the ``bucket brigade'') and propose some proof-of-principle implementations, which show that, in principle, only O(n) two-qubit physical interactions need take place during each qRAM call. That is, although a qRAM needs O(2n) quantum logic gates, only O(n) need to be activated during a memory call. The resulting decrease in resources could give rise to the construction of large qRAMs that could operate without the need for extensive quantum error correction.