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Prabha Mandayam
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Prabha Mandayam
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Prabha Mandayam
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Mandayam, Prabha
Mandayam, P.
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6 results
Now showing 1 - 6 of 6
- PublicationQubits through queues: The capacity of channels with waiting time dependent errors(01-02-2019)
; ; We consider a setting where qubits are processed sequentially, and derive fundamental limits on the rate at which classical information can be transmitted using quantum states that decohere in time. Specifically, we model the sequential processing of qubits using a single server queue, and derive explicit expressions for the capacity of such a 'queue-channel.' We also demonstrate a sweet-spot phenomenon with respect to the arrival rate to the queue, i.e., we show that there exists a value of the arrival rate of the qubits at which the rate of information transmission (in bits/sec) through the queue-channel is maximised. Next, we consider a setting where the average rate of processing qubits is fixed, and show that the capacity of the queue-channel is maximised when the processing time is deterministic. We also discuss design implications of these results on quantum information processing systems. - PublicationSecurity with 3-Pulse Differential Phase Shift Quantum Key Distribution(19-09-2018)
;Ranu, Shashank Kumar ;Shaw, Gautam Kumar; 3-pulse DPS-QKD offers enhanced security compared to conventional DPS-QKD by decreasing the learning rate of an eavesdropper and unmasking her presence with an increased error rate upon application of intercept and resend attack. The probability of getting one bit of sifted key information using beamsplitter attack also reduces by 25% in our implentation compared to normal DPS. - PublicationThe Classical Capacity of a Quantum Erasure Queue-Channel(01-07-2019)
; ; We consider a setting where a stream of qubits is processed sequentially. We derive fundamental limits on the rate at which classical information can be transmitted using qubits that decohere as they wait to be processed. Specifically, we model the sequential processing of qubits using a single server queue, and derive expressions for the classical capacity of such a quantum 'queue-channel.' Focusing on quantum erasures, we obtain an explicit single-letter capacity formula in terms of the stationary waiting time of qubits in the queue. Our capacity proof also implies that a 'classical' coding/decoding strategy is optimal, i.e., an encoder which uses only orthogonal product states, and a decoder which measures in a fixed product basis, are sufficient to achieve the classical capacity of the quantum erasure queue-channel. More broadly, our work begins to quantitatively address the impact of decoherence on the performance limits of quantum information processing systems. - Publication3 pulse differential phase shift quantum key distribution with spatial, or time, multiplexed(08-09-2019)
;Shaw, G. K. ;Shyam, S. ;Foram, S. ;Ranu, S. K.; We demonstrated 3 pulse differential phase shift quantum key distribution with 30 km quantum channel with two different approaches, namely path superposition and time bin superposition. - Publication3 pulse differential phase shift quantum key distribution with spatial, or time, multiplexed(01-01-2019)
;Shaw, G. K. ;Shyam, S. ;Foram, S. ;Ranu, S. K.; We demonstrated 3 pulse differential phase shift quantum key distribution with 30 km quantum channel with two different approaches, namely path superposition and time bin superposition. - PublicationDifferential phase encoding scheme for measurement-device-independent quantum key distribution(01-02-2019)
;Ranu, Shashank Kumar; This paper proposes a measurement-device-independent quantum key distribution (MDI-QKD) scheme based on differential phase encoding. The differential phase shift MDI-QKD (DPS-MDI-QKD) couples the advantages of DPS-QKD with that of MDI-QKD. The proposed scheme offers resistance against photon number splitting attack and phase fluctuations as well as immunity against detector side-channel vulnerabilities. The design proposed in this paper uses weak coherent pulses in a superposition of three orthogonal states, corresponding to one of three distinct paths in a delay-line interferometer. The classical bit information is encoded in the phase difference between pulses traversing successive paths. This 3-pulse superposition offers enhanced security compared to using a train of pulses by decreasing the learning rate of an eavesdropper and unmasking her presence with an increased error rate upon application of intercept and resend attack and beamsplitter attack. The proposed scheme employs phase locking of the sources of the two trusted parties so as to maintain the coherence between their optical signal, and uses a beamsplitter (BS) at the untrusted node (Charlie) to extract the key information from the phase encoded signals.