Classical non-perturbative simulations of open quantum systems' dynamics face several scalability problems, namely, exponential scaling of the computational effort as a function of either the time length of the simulation or the size of the open system. In this work, we propose the use of the Time Evolving Density operator with Orthogonal Polynomials Algorithm (TEDOPA) on a quantum computer, which we term as Quantum TEDOPA (Q-TEDOPA), to simulate non-perturbative dynamics of open quantum systems linearly coupled to a bosonic environment (continuous phonon bath). By performing a change of basis of the Hamiltonian, the TEDOPA yields a chain of harmonic oscillators with only local nearest-neighbour interactions, making this algorithm suitable for implementation on quantum devices with limited qubit connectivity such as superconducting quantum processors. We analyse in detail the implementation of the TEDOPA on a quantum device and show that exponential scalings of computational resources can potentially be avoided for time-evolution simulations of the systems considered in this work. We applied the proposed method to the simulation of the exciton transport between two light-harvesting molecules in the regime of moderate coupling strength to a non-Markovian harmonic oscillator environment on an IBMQ device. Applications of the Q-TEDOPA span problems which can not be solved by perturbation techniques belonging to different areas, such as the dynamics of quantum biological systems and strongly correlated condensed matter systems.
Some Notes Concerning the Dynamics of Noncommutative Lumps Corresponding to Nontrivial Vacua in Noncommutative Yang--Mills Models which are perturbative branches of M(atrix) Theory
Realization of Quantum Digital Signatures without the requirement of quantum memory
数字签名被广泛用于为电子通信提供安全性，例如在金融交易和电子邮件中。然而，目前使用的经典数字签名方案仅提供依赖于未经证明的计算假设的安全性。相比之下，量子数字签名（QDS）提供基于量子力学定律的信息理论安全性（例如Gottesman和Chuang 2001）。在这里，防止伪造的安全性依赖于不可能完全区分非正交的量子态。然而，以前的QDS方案的一个严重缺点是它们需要长期的量子存储器，这使得它们在实践中不可行。我们提出了一个方案的第一个实现（Dunjko et al 2013），它不需要量子存储器，并且只使用标准的线性光学元件和光电探测器。为了实现这一点，接收者使用新型的量子测量、量子态消除来测量分布式量子签名状态（例如，Barnett 2009，Bandyopadhyay等人2013）。这大大推进了QDS作为一种具有实际应用潜力的量子技术。
Hybrid digital-analog protocols for simulating quantum multi-body interactions
Cornell University（康奈尔大学）；University of Maryland（马里兰大学）；NIST（美国国家标准与技术研究院）；Joint Center for Quantum Information and Computer Science, NIST/University of Maryland（量子信息与计算联合中心，美国国家标准与技术研究院/马里兰大学）；Joint Quantum Institute, NIST/University of Maryland（量子联合研究所，美国国家标准与技术研究院/马里兰大学）；Duke University（杜克大学）；King's College London（伦敦国王学院）
