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arXiv 2017年

作者： Majumdar, Ritajit Sur-Kolay, Susmita Advanced Computing and Microelectronics Unit Indian Statistical Institute India

Quantum states have high affinity for errors and hence error correction is of utmost importance to realise a quantum computer. Laflamme showed that 5 qubits are necessary to correct a single error on a qubit. In a Pauli error model, four different types of errors can occur on a qubit. Maximally entangled states are orthogonal to each other and hence can be uniquely distinguished by a measurement in the Bell basis. Thus a measurement in Bell basis and a unitary transformation is sufficient to correct error in Bell states. However, such a measurement is not possible for non-maximally entangled states. In this work we show that the 16 possible errors for a non-maximally entangled two qubit system map to only 8 distinct error states. Hence, it is possible to correct the error without perfect knowledge of the type of error. Furthermore, we show that the possible errors can be grouped in such a way that all 4 errors can occur on one qubit, whereas only bit flip error can occur on the second qubit. As a consequence, instead of 10, only 8 qubits are sufficient to correct a single error. We propose an 8-qubit error correcting code to correct a single error in a non-maximally entangled state. We further argue that for an n-qubit non-maximally entangled state of the form a |0)0n+ ß |1)0n, it is always possible to correct a single error with fewer than 5n qubits, in fact only 3n + 2 qubits suffice. Copyright © 2017, The Authors. All rights reserved.

关键词： Quantum entanglement

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Homogeneously Representable Interval Bigraphs

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Electronic Notes in Discrete Mathematics 2003年 15卷 75-78页

作者： Das, Sandip Talukdar Malay Sen, P. Advanced Computing and Microelectronics Unit Indian Statistical Institute Kolkata 700 108 India Dept. of Mathematics University of North Bengal Darjeeling 734 430 West Bengal India

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Exploiting degeneracy to construct good ternary quantum error correcting code

arXiv

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arXiv 2020年

作者： Majumdar, Ritajit Sur-Kolay, Susmita Advanced Computing & Microelectronics Unit Indian Statistical Institute India

Quantum error-correcting code for higher dimensional systems can, in general, be directly constructed from the codes for qubit systems. What remains unknown is whether there exist efficient code design techniques for higher dimensional systems. In this paper, we propose a 7-qutrit error-correcting code for the ternary quantum system and show that this design formulation has no equivalence in qubit systems. This code is optimum in the number of qutrits required to correct a single error while maintaining the CSS structure. This degenerate CSS code can (i) correct up to seven simultaneous phase errors and a single bit error, (ii) correct two simultaneous bit errors on pre-defined pairs of qutrits on eighteen out of twenty-one possible pairs, and (iii) in terms of the cost of implementation, the depth of the circuit of this code is only two more than that of the ternary Steane code. Our proposed code shows that it is possible to design better codes explicitly for ternary quantum systems instead of simply carrying over codes from binary quantum systems. Copyright © 2020, The Authors. All rights reserved.

关键词： Quantum optics

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Approximate Ternary Quantum Error Correcting Code with Low Circuit Cost

Approximate Ternary Quantum Error Correcting Code with Low C...

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International Symposium on Multiple-Valued Logic

作者： Ritajit Majumdar Susmita Sur-Kolay Advanced Computing and Microelectronics Unit Indian Statistical Institute Kolkata

ISBN: (数字)9781728154060

ISBN: (纸本)9781728154077

Quantum error correcting code (QECC) with encoding and decoding circuits having low gate count, is an important criterion for realizing quantum computing systems. CSS QECCs are known to have simple circuits. Shaw et al. showed that it is not possible to have a 6-qubit CSS type QECC without sharing entanglement between the encoder and the decoder. In this paper, we propose a 6-qutrit approximate QECC (AQECC) of CSS structure which can simultaneously correct phase errors in upto six qutrits, and one bit error in only four of the six qutrits, without sharing prior entanglement. Our AQECC corrects a single error with probability 0.75 for symmetric error model, and probability 0.9988 for asymmetric error model. It also maintains CSS structure without sharing prior entanglement. Furthermore, the quantum cost of a circuit for this AQECC is 55.72% less than that for the 9-qutrit exact QECC. Overall, low qutrit count, low cost circuit realization with low depth and the ability to correct multiple phase errors make our proposed AQECC a suitable candidate for real life quantum channels.

关键词： Cascading style sheets Qubit Encoding Quantum computing Error correction codes Logic gates Error correction

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Optimal Error Correcting Code For Ternary Quantum Systems

arXiv

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arXiv 2019年

作者： Majumdar, Ritajit Sur-Kolay, Susmita Advanced Computing & Microelectronics Unit Indian Statistical Institute India

Multi-valued quantum systems can store more information than binary ones for a given number of quantum states. For reliable operation of multi-valued quantum systems, error correction is mandated. In this paper, we propose a 5-qutrit quantum error correcting code and provide its stabilizer formulation. Since 5 qutrits are necessary to correct a single error, our proposed code is optimal in the number of qutrits. We prove that the error model considered in this paper spans the entire (3 × 3) operator space. Therefore, our proposed code can correct any single error on the codeword. This code outperforms the previous 9-qutrit code in (i) the number of qutrits required for encoding, (ii) our code can correct any arbitrary (3 × 3) error, (ii) our code can readily correct bit errors in a single step as opposed to the two-step correction used previously, and (iii) phase error correction does not require correcting individual subspaces. Copyright © 2019, The Authors. All rights reserved.

关键词： Many valued logics

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Editorial

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Microprocessors and Microsystems 2004年第8期28卷 401-402页

作者： Jayasree Dattagupta Nabanita Das Advanced Computing and Microelectronics Unit Indian Statistical Institute Kolkata 700-108 India

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Analyzing the Effect of Soft Handover on Handover Performance Evaluation Metrics under Load Condition

Analyzing the Effect of Soft Handover on Handover Performanc...

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作者： Panigrahy, Nitish K. Ghosh, Sasthi C. College of Information and Computer Sciences University of Massachusetts AmherstMA01003-9264 United States Advanced Computing and Microelectronics Unit Indian Statistical Institute Kolkata700108 India

With increasing popularity of wireless local area network (WLAN) and emerging real-time applications, seamless mobility has become one of the primary concerns. Hence, the choice of a proper handover algorithm is of utmost importance. Various performance evaluation metrics for handover algorithms have been proposed in this regard. We argue that in a multiple access point (AP) scenario, the load on each of the APs, the requested data rate of the mobile terminal, and the soft handover have significant impact on these metrics. In this paper, we present an analytical framework to measure various handover performance evaluation metrics under both load condition and soft handover for a specific data rate request. Our approach is based on finding the circular region centered around an AP within which the requested data rate can be satisfied. We have considered WLAN usage efficiency, handover failure probability, and unnecessary handover probability as evaluation metrics. We have analyzed the impact of load and soft handover on these metrics. The impact of velocity on these metrics has also been analyzed. We also have derived lower bounds on both handover failure probability and unnecessary handover probability by formulating the problem into three circle intersection problem. The circular coverage assumption used in the framework is also validated through simulation. © 1967-2012 IEEE.

关键词： Efficiency

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A Fast Community-based Approach for Discovering Anomalies in Evolutionary Networks 14

A Fast Community-based Approach for Discovering Anomalies in...

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14th International Conference on COMmunication Systems and NETworkS, COMSNETS 2022

作者： Ghoshal, Arnab Kumar Das, Nabanita Das, Soham Asutosh College Department of Computer Science Kolkata India Indian Statistical Institute Advanced Computing and Microelectronics Unit Kolkata India Microsoft Corporation RedmondWA United States

ISBN: (纸本)9781665421041

Many real-life networks such as social networks, biological networks, citation networks etc., are temporally evolving by nature. In general, the evolution takes place gradually with time. But occasionally, the nodes may exhibit anomalous behavior that is to be detected and reported in real time. In this work, for anomaly detection in evolutionary networks, an action based approach is followed taking into account the network topology. The network is represented as a temporal stream of weighted graphs, where edge weights stand for frequency or power of actions. A new definition of anomaly score is introduced for nodes based on its action history. To reduce the search space, the community structure of the graph is exploited. It has been shown that only the nodes having multiple community membership are enough to detect anomaly in a temporally evolving network with overlapping community structure. To the best of our knowledge, this is the first work to exploit the overlapping community structure of an evolutionary network to identify the graph snapshots containing anomalous events. Experimental studies on both synthetic and real-world evolutionary networks show that the proposed technique achieves almost 16% improvement in F-Score compared to the state-of-the-art algorithms. Moreover, parallel implementation of the proposed technique results nearly 10× speedup making it suitable for real time computation of anomaly in evolutionary networks. © 2022 IEEE.

关键词： Anomaly detection

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Validation of a DiffServ based QoS model implementation for real-time traffic in a test bed

Validation of a DiffServ based QoS model implementation for ...

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18th National Conference on Communications, NCC 2012

作者： Gan Chaudhuri, Sruti Kumar, C.S. Rajakumar, Ratnam V. Advanced Computing and Microelectronics Unit Indian Statistical Institute Kolkata - 700108 India Department of Mechanical Engineering Indian Institute of Technology Kharagpur - 721302 India Department of Electronics and Electrical Communication Engineering Indian Institute of Technology Kharagpur - 721302 India

ISBN: (纸本)9781467308168

This paper presents a DiffServ based adaptive QoS model for real-time interactive traffic in constrained bandwidth IP network without over provisioning the users. A WRR based QoS scheduling algorithm has been implemented to allocate the network resources to the users. A tuning parameter for VBR real-time traffic is also introduced in order to provide fair performance to the non real-time traffic as well. The QoS model is implemented at the transmitter edge of the network. Edge switches and routers are configured with the proposed algorithm. The simulation (using NS2) and experimental results (using a test bed with real time network scenario) are presented for validation of the proposed model. © 2012 IEEE.

关键词： Scheduling algorithms

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Joint Base Station and Reflector Placement in an urban mmWave Network

Joint Base Station and Reflector Placement in an urban mmWav...

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Communications and Networking (MeditCom), IEEE International Mediterranean Conference on

作者： Rathindra Nath Dutta Subhojit Sarkar Sasthi C. Ghosh Advanced Computing and Microelectronics Unit Indian Statistical Institute Kolkata India

Millimeter-wave (mmWave) technology is expected to be the backbone of future communication networks. However, for all its benefits, mmWave communication comes with its fair share of challenges. In this context, the obstacle free strict line-of-sight (LOS) requirement is one of the primary hurdles that has to be crossed. One way to deal with this problem is to densely deploy small range base stations, called gNBs, to overcome outage due to obstacles. Reflectors have been proposed to augment the transmission environment, and reflect mmWaves bypassing the obstacles. Evidently, they can be used to increase the coverage area that do not have LOS with the available gNBs. We argue that considering the placement of gNBs and reflectors independently may lead to suboptimal solution. In this paper, we consider an urban deployment scenario, and attempt to maximally cover it by jointly placing the gNBs and reflectors. Given the hardness of the joint problem, we first develop a set cover based greedy solution and also provide a linear programming (LP) relaxation based solution. With extensive simulations, we show that with fixed number of available gNBs and reflectors to be placed, both our joint placement solutions can achieve a larger coverage compared to an existing approach.

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