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"Balakrishnan, S"
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Characteristics, implementation, and applications of special perfect entanglers
In this paper, we discuss the characteristics of special perfect entanglers from a new perspective, present the results obtained from the implementation of special perfect entangler circuits using cross-resonance interaction, and discuss their applications. First, we show that the entangling power of a two-qubit gate is proportional to the mean squared length of the chords present in the argand diagram of squared eigenvalues of the nonlocal part of the gate, and derive the entangling characteristics of special perfect entanglers from the argand diagram associated with them. Next, we discuss the implementation of a single-parameter special perfect entangler circuit in an IBM quantum processor. We implement the circuit for nine different parameters using two methods. In the first method, we use two echoed cross-resonance gates for implementation, and in the second method, we use pulse-level programming to define the pulse sequence of part of the circuits. For a particular input state, we perform quantum state tomography, calculate state fidelity and concurrence of the output density matrices, and compare the results obtained in both methods of implementation. We also measure the average gate fidelity for the B gate circuit. We construct a universal two-qubit quantum circuit using the special perfect entangler circuit. This universal circuit can be used to generate all two-qubit gates in IBM quantum processors. We also show that
(
n
-
1
)
B gate circuits can be used to generate
n
-qubit GHZ and perfect W states. We generate three-qubit perfect W state in IBM quantum processor. Perfect W state generated using pulse-level programming shows better fidelity than the state generated using four echoed cross-resonance gates.
Graphical abstract
Journal Article
Mirror symmetry in the geometry of nonlocal two-qubit gates and universal two-qubit quantum circuits
We discuss the transformation of nonlocal two-qubit gates and symmetries possessed by Weyl chamber of two-qubit gates under mirror operation. We define the mirror operation as reflections about a specific set of planes of Weyl chamber in
c
-space which is spanned by Cartan coordinates. For the lines at the intersection of two specific reflecting planes, both the mirror operation and inverse operation cause the same transformation of Cartan coordinates. The point representing B-gate being the only common point to all reflecting planes, Cartan coordinates and all nonlocal characteristics of B-gate are invariant under mirror operation. In
g
-space which is spanned by local invariants, the mirror operation can be defined as parity transformation. With the point representing B-gate at the center of Weyl chamber, the mirror symmetry of Weyl chamber is apparent in
g
-space. In addition, we show that the gate typicality is a linear function of a local invariant and discuss its transformation under mirror operation. We also discuss the ability of a special perfect entangler (SPE) and its mirror gate to construct other nonlocal two-qubit gates and show that an SPE and its mirror together with local
y
-rotations can generate SWAP operation. Further, we propose universal two-qubit quantum circuits involving two applications of SPEs and local
y
-rotations. Finally, we propose a scheme to implement SPEs in ion-trap quantum computers which allows the usage of proposed universal two-qubit quantum circuits in quantum computation. We show that
B
-gate can generate all two-qubit gates in four applications with suitable single-qubit gates. In terms of implementation time,
B
-gate and one of the proposed universal two-qubit quantum circuits are advantageous over CNOT gate being used as entangling basis gate in ion-trap quantum computer.
Graphical abstract
Journal Article
Low Temperature Annealed Zinc Oxide Nanostructured Thin Film-Based Transducers: Characterization for Sensing Applications
The performance of sensing surfaces highly relies on nanostructures to enhance their sensitivity and specificity. Herein, nanostructured zinc oxide (ZnO) thin films of various thicknesses were coated on glass and p-type silicon substrates using a sol-gel spin-coating technique. The deposited films were characterized for morphological, structural, and optoelectronic properties by high-resolution measurements. X-ray diffraction analyses revealed that the deposited films have a c-axis orientation and display peaks that refer to ZnO, which exhibits a hexagonal structure with a preferable plane orientation (002). The thicknesses of ZnO thin films prepared using 1, 3, 5, and 7 cycles were measured to be 40, 60, 100, and 200 nm, respectively. The increment in grain size of the thin film from 21 to 52 nm was noticed, when its thickness was increased from 40 to 200 nm, whereas the band gap value decreased from 3.282 to 3.268 eV. Band gap value of ZnO thin film with thickness of 200 nm at pH ranging from 2 to 10 reduces from 3.263eV to 3.200 eV. Furthermore, to evaluate the transducing capacity of the ZnO nanostructure, the refractive index, optoelectric constant, and bulk modulus were analyzed and correlated. The highest thickness (200 nm) of ZnO film, embedded with an interdigitated electrode that behaves as a pH-sensing electrode, could sense pH variations in the range of 2-10. It showed a highly sensitive response of 444 μAmM-1cm-2 with a linear regression of R2 =0.9304. The measured sensitivity of the developed device for pH per unit is 3.72μA/pH.
Journal Article
Significance of Bell States Over Four-Qubit Entangled States in Quantum Bidirectional Direct Communication Protocols
The controller-independent quantum bidirectional direct communication (QBDC) protocol using Bell states is widely studied. In recent times, protocols have been proposed using four-qubit entangled states with the intention of increasing security. In this work, we compare the controller-independent QBDC protocol using Bell states with that of a protocol that exploits four-qubit entangled states. We observe that the same two-qubit protocol can be run on a four-qubit system without information leakage. The security offered is the same in both cases, but the quantum efficiency of the protocol is reduced in the case of four-qubit entangled states. We highlight the significance of the protocol using Bell states from the physical implementation point of view.
Journal Article
Significance of Controller Independent Bell state-based communication protocol
Quantum communication is a technique in which quantum information is transferred from one place to another. There are several quantum communication protocols, starting from quantum key distribution (QKD). The most popular of them is quantum dialogue (QD), which enables communicants to exchange their secret messages simultaneously. QD can be broadly classified into controller dependent and controller-independent protocols. In this work, we aim to analyze the various characteristics such as the quantum resource, the measurement used, the encoding rules, and the dishonesty of the controller of quantum dialogue protocols. From the analysis of the considered protocols, we have found that the controller-independent QD protocol can be preferred over the controller-dependent protocol.
Journal Article
Alterations of mucosal microbiota in the colon of patients with inflammatory bowel disease revealed by real time polymerase chain reaction amplification of 16S ribosomal ribonucleic acid
Alterations in microbial communities closely associated with the intestinal mucosa are likely to be important in the pathogenesis of inflammatory bowel disease (IBD). We examined the abundance of specific microbial populations in colonic mucosa of patients with ulcerative colitis (UC), Crohn's disease (CD) and controls using reverse transcription quantitative polymerase chain reaction (RT-qPCR) amplification of 16S ribosomal ribonucleic acid (16S rRNA).
RNA was extracted from colonic mucosal biopsies of patients with UC (32), CD (28) and patients undergoing screening colonoscopy (controls), and subjected to RT-qPCR using primers targeted at 16S rRNA sequences specific to selected microbial populations.
Bacteroides-Prevotella-Porphyromonas group and Enterobacteriaceae were the most abundant mucosal microbiota. Bacteroides and Lactobacillus abundance was greater in UC patients compared with controls or CD. Escherichia coli abundance was increased in UC compared with controls. Clostridium coccoides group and C. leptum group abundances were reduced in CD compared with controls. Microbial population did not differ between diseased and adjacent normal mucosa, or between untreated patients and those already on medical treatment. The Firmicutes to Bacteroidetes ratio was significantly decreased in both UC and CD compared with controls, indicative of a dysbiosis in both conditions.
Dysbiosis appears to be a primary feature in both CD and UC. Microbiome-directed interventions are likely to be appropriate in therapy of IBD.
Journal Article
Effect of Noise in the Quantum Bidirectional Direct Communication Protocol Using Non- maximally Entangled States
Possibility of using non-maximally entangled states in quantum bidirectional direct communication has been shown recently by Srikanth A and Balakrishnan (Quantum Inf. Process. 19:133, 2020) [1]. The effect of noise in this protocol is analyzed by considering amplitude and phase damping models. Suitable combinations of messages and initial states are identified to minimize the effect of noise in the protocol. Further, we have shown the possibility of demarking the effects due to noise and the intruder.
Journal Article
Entanglement versus Mixedness: A Study using the Output States of Quantum Deleting Machines
Our study examines the output states produced by deletion machines, including the Pati-Braunstein (PB) and our proposed deleting machine (DM). We study the specific form of maximally entangled mixed state (MEMS) and Werner state that achieve the highest entanglement for a given level of mixedness. These states are useful in quantum information tasks due to their optimal entanglement for a given mixedness. We considered various entanglement measures (concurrence and negativity) and mixedness measures (linear and von Neumann entropy). We compared the output state of our proposed deletion machine with MEMS and Werner state, finding that our machine creates states with higher mixedness, entanglement in certain input state
(
α
)
and entanglement parameter (
w
,
p
) ranges. The results indicate that our proposed deletion machine could be effectively utilized in quantum information applications, similar to MEMS and Werner states.
Journal Article
Influence of noise on a quantum game in the light of modified EWL scheme
Entanglement is the key feature that distinguishes a quantum game from its classical counterpart. In this direction, entangling operators and their role in quantizing a classical game have been a subject of interest lately. Using these operators, a modification to the much explored Eisert-Wilkens-Lewenstein (EWL) quantization scheme is proposed and studied. In the present work, this scheme is subjected to noise through amplitude damping mode, bit-flip noise, and a comparative study with a noiseless case is carried out. As a result, we find that in the absence of noise, the payoffs of the players are high and can be manipulated by an entangling operator. Whereas when the factor of noise is maximum, the payoff of the players reduces to zero, and more so, there is no role for an operator in such a condition. A leap from quantum to classical game must then occur through noise (at least in the case of amplitude damping), as the maximum noise kills the effect of entanglement. However, such an observation depends on the nature of the noisy channel. In the case of a bit-flip channel, the noise actually favors the players’ payoffs, albeit still depending on entanglement. The results presented in this work display the prowess of the modified EWL scheme.
Journal Article