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Experimental non-Markovian process characterisation and control on a quantum processor [article]

Gregory A. L. White, Charles D. Hill, Felix A. Pollock, Lloyd C. L. Hollenberg, Kavan Modi
2020 arXiv   pre-print
Finally, we turn these high fidelity predictions into an adaptive control technique for non-Markovian systems and demonstrate decoupling of a qubit interacting with another qubit with an unknown Hamiltonian  ...  With our technique, we demonstrate several applications: We first estimate a statistically significant lower-bound on memory size for all of the devices.  ...  The resulting non-Markovian dynamics includes more general errors that may be temporally correlated or dependent on broader environmental context [4] [5] [6] .  ... 
arXiv:2004.14018v1 fatcat:n46j2sbdlbdb3gb364ctpst2vq

Demonstration of non-Markovian process characterisation and control on a quantum processor

G. A. L. White, C. D. Hill, F. A. Pollock, L. C. L. Hollenberg, K. Modi
2020 Nature Communications  
Our results show this characterisation technique leads to superior quantum control and extension of coherence time by effective decoupling from the non-Markovian environment.  ...  Where noisy processes cannot be accounted for using standard Markovian techniques, our reconstruction predicts the behaviour of the devices with an infidelity of 10−3.  ...  The resulting non-Markovian dynamics includes more general errors that may be temporally correlated or dependent on broader environmental context [4] [5] [6] .  ... 
doi:10.1038/s41467-020-20113-3 pmid:33298929 fatcat:72xbsu4khjfrjnt4daanunpkqe

Fault-Tolerant Quantum Dynamical Decoupling

K. Khodjasteh, D. A. Lidar
2005 Physical Review Letters  
This is important for coherent control of quantum systems such as quantum computers.  ...  Here we introduce a method of recursively concatenated dynamical decoupling pulses, designed to overcome both decoherence and operational errors.  ...  The noisy quantum control problem.-The problem of faulty controls and decoherence errors in the context of QIP, as well as other quantum control scenarios [9] , can be formulated as follows.  ... 
doi:10.1103/physrevlett.95.180501 pmid:16383882 fatcat:6lzoprng3vcgfkzmq2wwd5bhim

Nonperturbative dynamical decoupling with random control

Jun Jing, C. Allen Bishop, Lian-Ao Wu
2014 Scientific Reports  
In a large parameter error region, the out-of-order control pulses work as well as the regular pulses for dynamical decoupling and dissipation suppression.  ...  This relaxes the operational requirements placed on quantum control experiments to a great deal.  ...  With high precision, we can control the average values of the parameters which characterize the sequence, but we cannot control the errors which occur on them or predict any occurrence in advance.  ... 
doi:10.1038/srep06229 pmid:25169735 pmcid:PMC4148650 fatcat:wciosdp4vjc2xdu6fg6owm3anq

Experimental observation of thermalisation with noncommuting charges [article]

Florian Kranzl, Aleksander Lasek, Manoj K. Joshi, Amir Kalev, Rainer Blatt, Christian F. Roos, Nicole Yunger Halpern
2022 arXiv   pre-print
We initiate the experimental testing of its predictions, with a trapped-ion simulator.  ...  This work bridges quantum many-body simulators to the quantum thermodynamics of noncommuting charges, whose predictions can now be tested.  ...  The long-time distance to ρ NATS is consistent with a bound predicted in [19] .  ... 
arXiv:2202.04652v1 fatcat:xdp3xzxejrfsto3rwpgirdkvnu

Limitations of Quantum Simulation Examined by Simulating a Pairing Hamiltonian Using Nuclear Magnetic Resonance

Kenneth R. Brown, Robert J. Clark, Isaac L. Chuang
2006 Physical Review Letters  
While the number of elementary quantum gates does scale polynomially with the size of the system, it increases inversely to the desired error bound ϵ.  ...  Quantum simulation uses a well-known quantum system to predict the behavior of another quantum system.  ...  Control errors in NMR quantum computation arise, for example, since single qubit gates require finite time For H1, π 2 pulses are applied to qubit c in parallel with those on a and b, and the decoupling  ... 
doi:10.1103/physrevlett.97.050504 pmid:17026087 fatcat:wmenda4qu5buzexxecvvlqbyxy

From many-body to many-time physics [article]

Gregory A. L. White, Felix A. Pollock, Lloyd C. L. Hollenberg, Charles D. Hill, Kavan Modi
2022 arXiv   pre-print
Multi-time quantum processes are endowed with the same richness as many-body physics, including temporal entanglement and well-defined causal structures.  ...  Our techniques are pertinent to generic quantum stochastic dynamical processes, with a scope ranging across condensed matter physics, quantum biology, and in-depth diagnostics of NISQ era quantum devices  ...  The former gives a coarse view on temporal correlations, but is an important benchmark for the feasibility of quantum error correction.  ... 
arXiv:2107.13934v4 fatcat:5baz4hddwjcqpp6ambjv3ppfiy

Non-Markovian memory in IBMQX4 [article]

Joshua Morris and Felix A. Pollock and Kavan Modi
2019 arXiv   pre-print
With this method, we estimate (i) the size of fluctuations in the performance of a gate, i.e., errors due to non-Markovianity; (ii) the length of the memory; and (iii) the total size of the memory.  ...  We measure and quantify non-Markovian effects in IBM's Quantum Experience.  ...  To maintain consistency, each single qubit gate always acts on qubit 1 (with numbering from 0-4) and each controlled-not (C X ) acts on qubit 0 with the control on qubit 1.  ... 
arXiv:1902.07980v1 fatcat:tuekabwq2zef7mjxjvulwgjgvm

Extracting Quantum Dynamical Resources: Consumption of Non-Markovianity for Noise Reduction [article]

Graeme D. Berk, Simon Milz, Felix A. Pollock, Kavan Modi
2021 arXiv   pre-print
With an explicit example, we show that our methods enable a more optimal exploitation of temporal correlations, and extend the timescales at which noise suppression is viable by at least two orders of  ...  One remarkable achievement in this direction is dynamical decoupling; it details a clear set of instructions for counteracting the effects of quantum noise.  ...  quantum error correction (QEC).  ... 
arXiv:2110.02613v1 fatcat:juuxmpupava63fk5axsbwewexq

Maximizing Information on the Environment by Dynamically Controlled Qubit Probes

Analia Zwick, Gonzalo A. Álvarez, Gershon Kurizki
2016 Physical Review Applied  
Applications of this protocol that combines dynamical control and estimation theory tools to quantum sensing are illustrated for a nitrogen-vacancy center in diamond used as a probe.  ...  By resorting to quantum estimation theory, we analytically find the ultimate bound on the precision of estimating key parameters of a broad class of ubiquitous environmental noises ("baths") which the  ...  Concurrently, the minimum relative error converges to ε(τ c , t opt ) predicted from the Cramer-Rao bound (Fig. 3b) .  ... 
doi:10.1103/physrevapplied.5.014007 fatcat:7qzy2iebnjgp5jizyoe77dz2he

Dynamical control of electron spin coherence in a quantum dot: A theoretical study

Wenxian Zhang, V. V. Dobrovitski, Lea F. Santos, Lorenza Viola, B. N. Harmon
2007 Physical Review B  
We investigate the performance of dynamical decoupling methods at suppressing electron spin decoherence from a low-temperature nuclear spin reservoir in a quantum dot.  ...  The controlled dynamics is studied through exact numerical simulation, with emphasis on realistic pulse delays and long-time limit.  ...  Developing and benchmarking strategies for decoherence suppression in spin nanosystems are of vital importance to various areas of quantum physics, from quantum control theory to quantum device technologies  ... 
doi:10.1103/physrevb.75.201302 fatcat:shocuuffi5hunmceiow5a6uloa

Information Theoretical Limits for Quantum Optimal Control Solutions: Error Scaling of Noisy Channels [article]

Matthias M. Müller, Stefano Gherardini, Tommaso Calarco, Simone Montangero, Filippo Caruso
2020 arXiv   pre-print
By using tools of information and quantum optimal control theory, we provide analytical bounds (information-time bounds) to characterize our capability to control the system when subject to arbitrary sources  ...  Moreover, since the presence of an external noise field induces an open quantum system dynamics, we also show that the results provided by the information-time bounds are in perfect agreement with the  ...  of the control error with the control modulation as predicted by the information theoretical bounds.  ... 
arXiv:2006.16113v1 fatcat:dlkjctdqyfhstcv44xhqblibue

Eigenvalue Measurement of Topologically Protected Edge states in Split-Step Quantum Walks

Thomas Nitsche, Tobias Geib, Christoph Stahl, Lennart Lorz, Christopher Cedzich, Sonja Barkhofen, Reinhard F Werner, Christine Silberhorn
2019 New Journal of Physics  
To this end, we experimentally realise for the first time a split-step quantum walk with decoupling, which allows for investigating the effect of a bulk-boundary while realising only a single bulk configuration  ...  Furthermore, the results show that investigating a bulk-boundary with a single bulk is experimentally feasible when decoupling the walk beforehand.  ...  The group at Hannover acknowledges support from the DFG with the SFB 1227 DQmat and from the ERC grant DQSIM.  ... 
doi:10.1088/1367-2630/ab12fa fatcat:nhfrh77tsjblfkdqvf34a2vy2y

Error Mitigation in Quantum Computers through Instruction Scheduling [article]

Kaitlin N. Smith, Gokul Subramanian Ravi, Prakash Murali, Jonathan M. Baker, Nathan Earnest, Ali Javadi-Abhari, Frederic T. Chong
2021 arXiv   pre-print
Quantum systems have potential to demonstrate significant computational advantage, but current quantum devices suffer from the rapid accumulation of error that prevents the storage of quantum information  ...  Theoretical models, however, fail to capture all sources of noise in NISQ devices, making practical solutions necessary that better minimize the impact of unpredictable errors in quantum machines.  ...  Leveraging Dynamical Decoupling Dynamical Decoupling (DD) is an established error mitigation technique with similar inspirations as TS.  ... 
arXiv:2105.01760v2 fatcat:w56dhmhquzedlavlb6zyi6ml54

Controlling the Spontaneous Emission Rate of Single Quantum Dots in a Two-Dimensional Photonic Crystal

Dirk Englund, David Fattal, Edo Waks, Glenn Solomon, Bingyang Zhang, Toshihiro Nakaoka, Yasuhiko Arakawa, Yoshihisa Yamamoto, Jelena Vučković
2005 Physical Review Letters  
We observe large spontaneous emission rate modification of individual InAs Quantum Dots (QDs) in 2D a photonic crystal with a modified, high-Q single defect cavity.  ...  Compared to QDs in bulk semiconductor, QDs that are resonant with the cavity show an emission rate increase by up to a factor of 8.  ...  Using a streak camera with a temporal resolution of 20 ps, we measured A 650 ps [ Fig. 5(a) ].  ... 
doi:10.1103/physrevlett.95.013904 pmid:16090618 fatcat:g76t7xuleba7jopiaqyozpewce
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