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Quantum random-access memory (QRAM) is a mechanism to access data (quantum or classical) based on addresses which are themselves a quantum state. QRAM has a long and controversial history, and here we survey and expand arguments and…

Quantum Physics · Physics 2025-12-03 Samuel Jaques , Arthur G. Rattew

Quantum random access memory (QRAM) promises simultaneous data queries at multiple memory locations, with data retrieved in coherent superpositions, essential for achieving quantum speedup in many quantum algorithms. We introduce a…

Quantum Physics · Physics 2025-06-13 Zhaoyou Wang , Hong Qiao , Andrew N. Cleland , Liang Jiang

Quantum Random Access Memory (QRAM) is a critical component for loading classical data into quantum computers. While constructing a practical QRAM presents several challenges, including the impracticality of an infinitely large QRAM size…

A random access memory (RAM) uses n bits to randomly address N=2^n distinct memory cells. A quantum random access memory (qRAM) uses n qubits to address any quantum superposition of N memory cells. We present an architecture that…

Quantum Physics · Physics 2009-11-13 Vittorio Giovannetti , Seth Lloyd , Lorenzo Maccone

Efficient and coherent data retrieval and storage are essential for harnessing quantum algorithms' speedup. Such a fundamental task is addressed by a quantum Random Access Memory (qRAM). Despite their promising scaling properties, current…

Quantum Physics · Physics 2026-04-09 Giuseppe De Riso , Giuseppe Catalano , Seth Lloyd , Vittorio Giovannetti , Dario De Santis

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…

Quantum Physics · Physics 2022-10-31 Koustubh Phalak , Junde Li , Swaroop Ghosh

Quantum devices should operate in adherence to quantum physics principles. Quantum random access memory (QRAM), a fundamental component of many essential quantum algorithms for tasks such as linear algebra, data search, and machine…

Quantum Physics · Physics 2024-07-25 Yunfei Wang , Yuri Alexeev , Liang Jiang , Frederic T. Chong , Junyu Liu

Quantum computing is a rapidly expanding field with applications ranging from optimization all the way to complex machine learning tasks. Quantum memories, while lacking in practical quantum computers, have the potential to bring quantum…

Quantum random-access look-up of a string of classical bits is a necessary ingredient in several important quantum algorithms. In some cases, the cost of such quantum random-access memory (qRAM) is the limiting factor in the implementation…

Quantum Physics · Physics 2020-01-24 Olivia Di Matteo , Vlad Gheorghiu , Michele Mosca

Hybrid quantum systems in which acoustic resonators couple to superconducting qubits are promising quantum information platforms. High quality factors and small mode volumes make acoustic modes ideal quantum memories, while the qubit-phonon…

A quantum random access memory (qRAM) is considered an essential computing unit to enable polynomial speedups in quantum information processing. Proposed implementations include using neutral atoms and superconducting circuits to construct…

Quantum Physics · Physics 2021-08-11 Kevin C. Chen , Wenhan Dai , Carlos Errando-Herranz , Seth Lloyd , Dirk Englund

Quantum Random Access Memory (QRAM) is a crucial architectural component for querying classical or quantum data in superposition, enabling algorithms with wide-ranging applications in quantum arithmetic, quantum chemistry, machine learning,…

Quantum Physics · Physics 2025-03-04 Shifan Xu , Alvin Lu , Yongshan Ding

A "bucket brigade" architecture for a quantum random memory of $N=2^n$ memory cells needs $n(n+5)/2$ times of quantum manipulation on control circuit nodes per memory call. Here we propose a scheme, in which only average $n/2$ times…

Quantum Physics · Physics 2012-12-12 Fang-Yu Hong , Yang Xiang , Zhi-Yan Zhu , Li-zhen Jiang , Liang-neng Wu

Quantum random access memories (QRAMs) are pivotal for data-intensive quantum algorithms, but existing general-purpose and domain-specific architectures are hampered by a critical bottleneck: a heavy reliance on non-Clifford gates (e.g.,…

Quantum Physics · Physics 2025-10-07 Guangyi Li , Yu Gan , Zeguan Wu , Xueyue Zhang , Zheshen Zhang , Junyu Liu

Near-term quantum computers have been built as intermediate-scale quantum devices and are fragile against quantum noise effects, namely, NISQ devices. Traditional quantum-error-correcting codes are not implemented on such devices and to…

Quantum Physics · Physics 2024-03-18 Yusuke Hama , Hirofumi Nishi

Quantum random access memory (QRAM) is a central primitive for coherent data access in quantum algorithms, yet it remains controversial in practice because the wall-clock cost of "one lookup" can hide routing depth, control overhead, and…

Quantum Physics · Physics 2026-01-09 Leonardo Bohac

As standard data loading processes, quantum state preparation and block-encoding are critical and necessary processes for quantum computing applications, including quantum machine learning, Hamiltonian simulation, and many others. Yet,…

Quantum Physics · Physics 2025-12-18 Xiao-Ming Zhang

Quantum computers promise tremendous impact across applications -- and have shown great strides in hardware engineering -- but remain notoriously error prone. Careful design of low-level controls has been shown to compensate for the…

Proposals for quantum random access memory (QRAM) generally have a binary-tree structure, and thus require hardware that is exponential in the depth of the QRAM. For solid-state based devices, a fabrication yield that is less than $100\%$…

Quantum Physics · Physics 2024-11-26 D. K. Weiss , Shifan Xu , Shruti Puri , Yongshan Ding , S. M. Girvin

Quantum algorithm design usually assumes access to a perfect quantum computer with ideal properties like full connectivity, noise-freedom and arbitrarily long coherence time. In Noisy Intermediate-Scale Quantum (NISQ) devices, however, the…

Quantum Physics · Physics 2020-09-11 Xiangzhen Zhou , Sanjiang Li , Yuan Feng