Anil Kumar | |
|---|---|
.gif) | |
| Born | 25 June 1941 |
| Nationality | Indian |
| Alma mater | |
| Known for | Studies on Nuclear magnetic resonance spectroscopy |
| Awards |
|
| Scientific career | |
| Fields | |
| Institutions | |
| Doctoral advisor | ?? |
| Doctoral students | ?? |
Professor Anil Kumar (born 1941) is an Indian experimental physicist, known for
his work in the field of Nuclear Magnetic Resonance (NMR) Spectroscopy. He has
had the unique distinction of having worked with and contributed to the
research of two Nobel Laureates in the field of NMR, Prof. Richard Ernst and
Prof. Kurt Wuthrich. Prof Anil Kumar has over 150 research publications, has
trained several PhD students many of whom are well-established scientists, and
has established an internationally recognized research group on NMR methodology
at the Indian Institute of Science Bangalore. A fellow of all the three
National Science Academies of India and of the The World Academy of Sciences
Trieste, Prof. Anil Kumar is a also a recipient of the Sir C.V.Raman Medal
(Hari Om Trust of UGC) 1993, Platinum Jubilee Lecture Award of the Indian
Science Congress Association 1994, Prof. K. Rangadhama Rao Memorial Award of
INSA 1996, FICCI Award for Physical Sciences 1996-97, MSIL Chair at IISc
1994-97 and Alumni Award of IISc for Excellence in Research in Science 2000.
He also received the 2001 Goyal Award in Chemistry and the DAE-Raja Ramanna
Prize Lecture in Physics of JNCASR 2003. He held a Visiting Chair Chaire
Condorcet at Ecole Normale Superieure at Paris France in 1998 and Visiting
Professorships at University of North Carolina Chapel Hill USA 1989-90,
Indiana University Purdue USA 1994 and University of Michigan Ann Arbor
1998-99. After superannuation he was designated an Honorary Professor at IISc
Bangalore and currently NASI Honorary Scientist at IISc Bangalore.
Prof. Anil Kumar has several pioneering and major research contributions in the development of modern NMR methodology, which are responsible for the rapid growth of this field. He initially worked on the development of double-resonance NMR techniques for relaxation studies. During his stint in the laboratory of Prof. Richard Ernst at ETH Zurich Switzerland, he actively participated in the pioneering work on 2D NMR spectroscopy. He performed the very first 2D NMR experiment in liquids and hte first 2D Fourier imaging experiment (which is now widely used in Magnetic Resonance Imaging). He also applied two-dimensional NMR techniques to the study of biomolecules. He was the first one to apply the two-dimensional Nuclear Overhauser Effect (2D-NOE now known as NOESY) experiment to a biomolecule (this paper has over 1700 citations), which opened the field for the determination of three-dimensional structures of biomolecules in solution by NMR spectroscopy.
Biography
editAnil Kumar, born on 25 June 1941, is Indian Chemical Physicist. He did his college studies at Meerut College (Agra University) from where he graduated in 1959 and completed his master's degree in 1961. Then for three years, he worked at Meerut College as Lecturer in Physics (1961-64). After that, he joined Indian Institute of Technology Kanpur to pursue his Ph.D. and in 1969 he got his Ph.D. degree. He then moved to the USA for his post-doctoral studies where he spent one year at Georgia Institute of Technology, Atlanta and two years at the University of North Carolina. He also worked with Nobel Laureate Prof. Richard R. Ernst as a research associate (1973-76) and jointly with Prof. Ernst and Prof. Kurt Wüthrich (1979-80) at Swiss Federal Technical Institute, Zurich, Switzerland. He joined the Department of physics in January 1977 at Indian Institute of Science, Bangalore. He then was a Senior Scientific Officer (1977-82), Assistant Professor (1982-84), Associate Professor (1984-1990) and Professor (1990-2003) at IISc Bangalore. He also hold the position of Chairman of the Department of Physics (1994-97). At IISc, he got associated with the NMR facility as Resident-in-charge (1977-82), as Joint Convener (1984-94) and as Convener (1998-2003) and contributed towards making this Facility as one of the best in the country and well recognized internationally (currently houses 8 NMR spectrometers).
Scientific Achievement
editEstablishment of NMR Facilities in India
editProf. Anil Kumar returned from Zurich in 1977, to help establish the first superconducting magnet based High Field Fourier Transform NMR spectrometer in Indian Institute of Science (IISc) Bangalore, jointly with Prof. Khetrapal. Prof. Anil Kumar has [as Resident-in-charge (1977-82), as Joint Convener (1984-94) and as Convener (1998-2003)] contributed towards making this Facility as one of the best in the country and well recognized internationally (currently houses 8 NMR spectrometers). Additionally, he established at IISc, an internationally recognized research group on “NMR methodology”. As a result of the success of the NMR Facility in IISc, many more NMR facilities were established in the country and at the moment several of these other Facilities are headed by former students of Prof. Anil Kumar.
Highlights of Research Contributions
editPreamble
editProfessor Anil Kumar has several pioneering and major research contributions in the development of modern NMR methodology, which are responsible for the rapid growth of this field, recognized by the award of Nobel Prizes to Prof. Richard Ernst (1991) and Prof. Kurt Wüthrich (2002). Prof. Anil Kumar [with over a dozen publications with Prof. Ernst and nearly a dozen with Prof. Wüthrich (during 1974-84)] has contributed, often as a first author, the development, and application of many of the experiments. These include the very first two-dimensional NMR experiment and many more experiments. Prof. Anil Kumar also applied two-dimensional NMR to study of biomolecules. He was the first one to apply the two-dimensional Nuclear Overhauser Effect (2D-NOE now known as NOESY) experiment to a biomolecule (pub. No 30 with over 1700 citations), opening the field of NMR to the determination of three-dimensional structures of proteins in solution by NMR, eventually resulting in the above two Nobel Prizes.
In addition, Prof Anil Kumar has three other major contributions in NMR:
(i) MRI (Magnetic Resonance Imaging) has revolutionized human radiology. Prof. Anil Kumar made the fundamental contribution to this area. His Fourier-NMR-Imaging method (…), which utilizes the magnetization most efficiently, is the preferred method in clinical MRI (and is used in every clinical MRI all over the world).
(ii) Separated Local Field (SLF) Spectroscopy in Solid-State NMR: Prof. Anil Kumar was the first to observe oscillations in cross-polarization dynamics in solid-state NMR (12). These oscillations arise from a dominant dipolar coupling and eventually became the source of distance information in solid-state NMR. This experiment and its variances, known as “Separated Local Field (SLF) Spectroscopy” became the backbone of solid-state NMR and is used in every study of bio-molecules by solid-state NMR.
(iii) Quantum Computing by NMR:
In recent years there have been exciting developments in the field of Quantum Computing. NMR is also one of the techniques being exploited in this new emerging very exciting area. Prof. Anil Kumar started experimental work in this area in 1999 has made significant contributions with nearly 50 publications and 8 Ph.D.’s in this field. His group pioneered experimental work in this field, in India.
Other Research Contributions
edit1. Development in the methodology of two-dimensional NMR:
Prof. Anil Kumar has continued development of new experiments in two-dimensional NMR spectroscopy and their applications. He developed the modified Z-COSY two-dimensional experiment and demonstrated that this can be utilized for obtaining the energy-level diagrams of complex spin systems in NMR. He has then applied this methodology for obtaining information on energy levels of several molecules oriented in liquid crystal matrices. This method is now being exploited for delineating the energy levels of oriented molecules for using them for quantum computing by NMR (Pub Nos. 98, 105, 106, 149).
2. Cross-correlations in NMR Spectroscopy:
Whenever more than one mechanism is responsible for the relaxation of nuclear spins, there are possibilities of existence of cross-terms between them known as cross-correlations. Prof. Anil Kumar has spent considerable effort, in investigating the effects of cross-correlations in the longitudinal and transverse relaxation of coupled spins in NMR. He has found experimental evidence of “multiplet effect” arising from cross-correlations in longitudinal relaxation of protons, carbons and fluorine nuclei. These are ascribable to cross-terms between the chemical shift anisotropy relaxation of these nuclei with the dipolar relaxation with nearby protons. Prof. Anil Kumar has also analyzed in detail the influence of cross-correlations on saturation transfer experiments, known as nuclear Overhauser (NOE) in several spins, systems, especially in three, four and five spin systems, in the linear configuration. It is found that while there is a large multiplet effect of cross-correlations, there is also a significant net effect. The net effect is analyzed in further details and it is found that except in some small range of correlation time regime, the net effect is small. The net effect affects the distance estimation algorithm of biomolecular structure determination by NMR and hence this is of considerable importance. Small longitudinal cross-correlations have also been detected by separating out certain relaxation pathways by use of rapid 180? pulses during the relaxation dynamics of coupled spins. Longitudinal cross-correlations have also been investigated in fluorinated benzenes and it is found that the magnitude and orientation of the fluorine chemical shift anisotropy tensor are strongly dependent on the ortho-substitution, in conformity with earlier observations in the solid state. This is the first such observation through liquid state NMR. (Pub Nos. 102, 109, 111, 118, 122, 126, 128, 131).
Prof. Anil Kumar has also investigated the effect of cross-correlations in transverse relaxation via explicit calculation of the line widths/decay rates of single and multiple quantum coherences in coupled spins in liquid state NMR. He found that cross-correlations contribute differential widths to the various line of a multiplet, sometimes retaining, but often breaking the symmetry of the multiplets. Effect of strong coupling was also investigated in detail. Prof. Anil Kumar analyzed the effect of what he terms as “Remote Cross-correlations”, on line widths of coupled spins. He found that remote cross-correlations contribute a first-order differential line width to the various lines of a J-split multiplet, and second-order effects in absence of J, but the presence of some direct cross-correlations (Pub Nos. 110, 112, 116).
The study of cross-correlations has seen some very significant developments, in recent years in biomolecular NMR and effects such as “TROSY” have been invented, which extend the range and size of biomolecules that can be studied by liquid state NMR. The cross-correlation work of Prof. Anil Kumar has been duly recognized by the international community and he has written a comprehensive and authoritative, invited review on this subject in “Progress in NMR Spectroscopy” published by Elsevier Science (Pub. No. 127). This review is extremely well cited.
Bloch Equations Revisited
editProf. Anil Kumar, along with one of his student has ab-intio re-solved the phenomenological Bloch Equations, in presence of an off-resonance r.f. field, by redefining the various constants, such that these solutions, unlike earlier solutions, are valid for r.f. field tending to zero. Another feature of these solutions is that the evolution of the initial state magnetization and that of the steady-state magnetizations have been separated out yielding new insight into the solutions of the Bloch Equations. It is shown that the initial state magnetization evolves, in general, in biexponential oscillatory manner, and ultimately decay to zero. The steady-state magnetization, on the other hand, grows independently from zero, also in a biexponential oscillatory manner, reaching its steady-state value. He has further shown that it is possible to separate out the contributions of the initial state and steady state magnetization components by the use of two-dimensional NMR spectroscopy. This work has been much appreciated (Pub. Nos. 108,117).
Solid State NMR
editProf. Anil Kumar’s contributions to solid-state NMR can be grouped into two fields which eventually overlap.
(i) Side band suppression in Magic Angle Sample Spinning NMR:
Magic Angle Spinning (MAS) of powder samples gives rise to sharp resonances in solids and has contributed tremendously to the development of the field of solid-state NMR of powder samples. One of the problems in this spectroscopy is the appearance of spinning side bands at multiple of spinning frequencies. Pulse methods have been developed in literature for suppression of such spinning side bands. However, these pulse methods are too complex for routine application. Prof. Anil Kumar has suggested a computer controlled method for suppression of side bands in such spectra, in which the spinning speed is varied during the course of the experiment, leading to coherent averaging of the center bands as opposed to side bands, leading to the effective dispersion of side bands into noise. He has applied the method to both one and two-dimensional NMR spectroscopy (Pub. Nos. 115, 125).
(ii) NQR Spectroscopy:
Prof. Anil Kumar has during this period started the field of two-dimensional NQR spectroscopy and obtained nutation 2D NQR spectra of single crystals, leading to a detailed study of the off-resonance dependence of such spectra (Pub No. 119). Based on this experiment, he started the field of NQR imaging of solid samples. This is an interesting field, in which solid samples can be imaged, by a non-destructive method. Initial experiments have been performed which show promise. Multiple-quantum magic angle spinning (MQMAS) spectroscopy of quadrupolar nuclei is a promising field, which yields sharp resonance of the highest quantum resonance in a two-dimensional experiment. Such spectroscopy has been developed and optimization of experimental pulse methods achieved (Thesis: T.G. Ajith Kumar).
Other Developments in NMR
edit(i) A fast method for measurement of long spin-lattice relaxation times by a single scan inversion recovery experiment
A new method for measurement of long spin-lattice relaxation times (T1) has been proposed. In this method, the magnetization of the whole sample is inverted by a non-selective 180° pulse and during its recovery, the magnetization of differently selected slices is monitored as a function of a variable delay by using a linear gradient and frequency selective 90° pulses. Thus the entire inversion-recovery curve is mapped out in a single inversion, resulting in substantial saving in experimental time. This work is published in J. of Magn. Reson., 383, 99-103 (2004), (Pub. No. 147).
(iii) Implementation of parallel search algorithms using spatial encoding Using spatial encoding and multi-frequency pulse, bits of information can be stored in NMR. Using five consecutive bits various alphabets can be encoded and a sentence can be written. Parallel search for a particular alphabet can then be performed by repeatedly writing the searched alphabet and taking a difference spectrum. On summing the five bits, the searched letter has the null intensity and the letter with the complementary code has maximum intensity. The remaining alphabets have variable intensity depending on the number of differences between their codes and the code of the searched alphabet. This algorithm is demonstrated using 215 bits of information. This work is published in Physical Review A, 71, 042307 (2005),; (Pub. No. 156).
(iv) Study of Spin-Diffusion in Biomolecule: Transport of magnetization in a biomolecule was earlier described as a diffusion along a linear chain of equidistant spins. In this work, this model is extended to include diffusion in a bi-spaced one-dimensional lattice. It is found that the driven NOE experiment can still be described by a diffusion equation. Such a bi-spaced linear lattice is expected in an extended ?-sheet protein in which all side chains proton are deuterated. This work is published in J. Magn. Reson. 181, 112-117 (2006); (Pub/ No. 162)
Quantum Computing by NMR
editIn recent years there have been exciting developments in the field of quantum computing. It has been shown that quantum-mechanical systems, have inherent capabilities of massive parallel processing, which may someday solve problems, too difficult or unsolvable by classical computations. This has generated a lot of excitement among quantum physicist on one hand and computational scientists on the other. High-resolution NMR of liquid samples promises one of the possible candidates for such work. Prof. Anil Kumar has initiated research in this area and has demonstrated experimentally, a distillation of pseudo-pure states, implementation of logical operations and gates on 2,3 and 4 bit systems as well as implemented 2 and 3-qubit Deutsch-Jozsa quantum algorithm, using one and two-dimensional NMR spectroscopy. Quantum state Tomography, use of quadrupole nuclei and dipolar coupled nuclei in molecules oriented in liquid crystal matrices have been exploited leading to benchmarking of up to 8 qubit system. Use of 600 metric phase in NMR QC has been demonstrated in several systems. Local adiabatic evolution algorithm and mixed state, geometric phase in quantum interferometry have been demonstrated. Quantum games are also being implemented by NMR. Specifically, the various contributions in NMR Quantum Information Processing and NMR QC are:
(i) Preparation of Pseudo Pure States
Many algorithms in QC require an initial “pure” state. In NMR based QC, we can prepare only a “pseudo-pure-state” (PPS), which mimics a “pure” state. Several methods have been developed in the literature. In his laboratory this has been achieved by using spatial averaging [163, 167], temporal averaging [Mahesh (Thesis)], logical labeling [124, 129] and by using multi-frequency pulses [160]. In addition, we have also suggested a novel method, named “Spatial Averaged Logical Labeling Technique (SALLT)”, which does not scale with the number of qubits [134]. In this method, Prof. Anil Kumar and his group uses a labeling qubit and divide the entire system into two sub-systems based on the spin state of the labeling qubit. A Hadamard transform followed by the gradient pulse equalizes the populations of all states within each sub-system to two different values. A single transition selective pulse then creates the desired subsystem PPS [134]. This work has been much appreciated and being used by many others.
Prof. Anil Kumar and his group also extensively utilized the method of preparation of Pair Of Pseudo-pure States (POPS), suggested by Fung et al, in several of our work in which dipolar coupled spins have been used [145, 149, 151, 164]. This method is extremely useful in strongly coupled spin systems and in quadrupolar systems, where the individual spins cannot be treated as individual qubits and the 2N energy levels are collectively treated as an N-qubit system.
(ii) Logic Gates
Prof. Anil Kumar and his group implemented several reversible logical-gates using both one-dimensional (1D) and two-dimensional (2D) NMR experiments. For example, our figure containing a complete set of 24, 2-qubit reversible one-to-one 2D gates, appeared on the cover of the January 2001 issue of Journal of Magnetic Resonance [130]. In addition they have implemented 3-qubit 1D and 2D gates and have demonstrated execution of several gate operation in one unitary transform [124, 129, 130]. The half-adder and subtractor operation in the 3-qubit system and full adder in the 4-qubit system have also been implemented [137, 148]. Inversion-on-equality gate, Parity gate, and Fan-out gates have been implemented in three different weakly coupled 3-qubit systems [150].
(iii) Algorithms
Prof. Anil Kumar and his group have implemented Deutsch-Jozsa (DJ) algorithm in many systems [124, 129, 130, 132, 135, 139, 143, 145, 151, 157, 160, 163]. This quantum algorithm can test in a single query, whether a function of several parameters is “Constant” or “Balanced” as opposed to the classical method which needs several queries. This algorithm has been used by us basically as a test bed for a new qubit system that we use in various situations such as coupled spin ½ nuclei in weak or strong coupling, quadrupolar nuclei, dipolar coupled spins with or without symmetry.
They have also implemented Grover’s search algorithm in several systems [140, 142, 151, 157]. Grover’s search algorithm uses coherent equal superposition as an initial state and can search an unsorted database much faster than the classical search algorithms. They have also used this algorithm for testing our tomography method in which the various stages of the algorithm were tomography to check on the evolution of the density matrix during the algorithm [142].
(iv) Tomography:
The readout of the density matrix is known as tomography. Prof. Anil Kumar and his group have suggested the use of multiple-quantum 2D NMR spectroscopic method for simultaneous measurements of all the off-diagonal elements of the density matrix [140, 142], rather than selective experiments suggested earlier in the literature by others. This method has the advantage that all non-observable elements of the density matrix (multiple-quantum elements) can be detected in one set of experiment, rather than individual experiments for each non-observable element. This method has been extensively used by us and others for checking (a) the preparation of a state, (b) the progress of an algorithm at its various stages and (c) for reading the final result of the algorithm [140]. Unlike other methods which use spin (qubit) selective pulses, this method can be used for all systems, including dipolar and quadrupolar systems, systems for which qubit addressability is not possible [149].
(v) Geometric (Berry) Phase:
Prof. Anil Kumar and his group have demonstrated observation and use of “geometric” phase in NMR QC. When a vector is a parallel transported on a curved surface in a cyclic manner, it acquires a “geometric” phase (also known as Berry’s phase) in addition to a “dynamical” phase. The “geometric” phase depends only on the solid angle subtended by the path at the center of the sphere and not on the details and the speed of the path and thus is “fault tolerant”. This phase has been observed in optics and also in conventional NMR. They have developed a protocol, where this phase can be observed by the use of transition selective ? or ?/2 pulses which are phase shifted with respect to each other. The solid angle in such experiments is then depended on the phase shift. They have incorporated the geometric phase in quantum information processing protocols that they have implemented using transition selective pulses in weakly as well as strongly dipolar coupled spin systems [157, 159, 161, 163]. In the later case it has been demonstrated that pairs of energy levels can be treated as “fictitious” spin ½ sub-systems and the coherence associated with this pair of levels can be transported on a Bloch sphere using transition selective pulses, yielding the desired geometric phase. The dynamical phase is re-focused in our experiments by the use of “Hahn Echoes”. Using such geometric phases, controlled phase shift gates have been implemented [161, 163]. Several algorithms have been implemented by us by using geometric phases in NMR QC. These include the DJ, Parity and Grover’s search algorithms [163].
In his another work, mixed state geometric phase has been studied [159]. De-coherence plays an important role in all QC. In particular, it leads a pure state to a mixed state. It is therefore advantageous to study geometric phase in mixed state systems. In a first experimental study of its kind, they have studied the dependence of interference visibility and shift of the pattern, on mixed state geometric phase by NMR [159].
(vi) Lifetime of pseudo-pure-state:
In a pioneering study, Prof. Anil Kumar and his group have measured the lifetime of pseudo-pure-states and demonstrated that cross-correlations in two competing relaxation pathways differentially retard the relaxation of some pseudo-pure-states and enhance that of other [153]. This is important in the context of “use of long-lived states for information storage”. This is also part of the current ongoing research, where they are investigating symmetry preserving relaxation processes in NMR with eventual applications in NMR QC.
(vi) Search for higher qubit systems:
Most of NMR based QIP has been carried out by using molecules in isotropic solution, in which the qubits are formed between nuclear spins which have indirect spin-spin coupling mediated through the covalent bonds. These couplings are small in value and limited to a few bonds only. In order to search for a higher number of qubits in NMR we have been exploiting the use of first-order quadrupolar coupling in nuclei with spin > ½ and dipolar coupling among spin ½ nuclei, by partially orienting molecules in liquid crystal matrices.
a. Quadrupolar Nuclei:
Prof. Anil Kumar and his group have demonstrated benchmarking of spin 3/2 and 7/2 nuclei respectively as 2 and 3 qubit systems [133, 137, 138, 143, 160]. Gate operations, preparation of pseudo-pure state and DJ algorithm have also been implemented in such systems. In Cs-133 (a spin 7/2 nucleus) oriented in a liquid crystal matrix, half adder and subtraction operations have been carried out using “optimum labeling of the states”. It was found that if one uses an “optimum” labeling scheme rather than a “conventional” labeling of the energy levels, one can significantly reduce the number of transition selective pulses needed for a given algebraic operation. The optimum labeling scheme was initially found by “trial and error” [137]. Later, they found a systematic method based on “set” theory to find the optimum labeling of energy states [148]. This optimum labeling method was used in a 4-qubit system of spin ½ nuclei to implement a full-adder operation [148].
A spin 1 nucleus, oriented in a liquid crystal matrix, has three unequally spaced energy levels, gives two lines and can be treated as a single qutrit system. In a pioneering study, they have experimentally demonstrated the benchmarking of such a system by using a deuterium nucleus oriented in a liquid crystal matrix. Preparation of pseudo-pure states and a complete set of gate operations have been performed [146].
b. Dipolar Coupled Spins.
Dipolar coupling among oriented molecules lead to strongly coupled spins. The first task in such cases is the identification of each transition to a pair of energy level. Prof. Anil Kumar and his group have used a Z-COSY 2D experiment, which we had developed in 1992 for such a purpose (not having any idea of QC at that time). This important experiment has now been used to obtain the energy level diagram of 3, 4, 5 and 8 spin systems [136, 138, 145, 149, 164]. They have demonstrated that these systems can then respectively be used as 3, 4, 5 and 8 qubit systems. CN- NOT gate operation, preparation of pair-of-pseudo-pure states (POPS) and controlled SWAP operations have been carried out. In the 5 qubit system, we have also performed entanglement of two-qubits and entanglement transfer to other two qubits by controlled SWAP operation using transition selective pulses [149].
The Z-COSY algorithm is fully automated and is being exploited for the search for higher qubit system. The highest number of qubits achieved by this method in our laboratory is 8 qubits. The molecule used is mono-fluoro-naphthalene oriented in a liquid crystal. In such case, all intra-molecular dipolar couplings are retained, scaled down by the order parameter. The 7 protons in the molecule become strongly coupled and one obtains nearly 500 proton and 125 fluorine transitions in the 1D spectra of this molecule [164]. All these have been fully assigned by the use of a Hetero-nuclear version of the Z-COSY experiment, also developed in our laboratory for this purpose. Controlled-NOT, POPS, SALLT and controlled SWAP operations have been successfully performed in this molecule [164]. This is being highly appreciated by the international magnetic resonance community.
(vii) Quantum Games and other Problems in QC:
Experimental implementation of Quantum Ulam’s game has been performed by Prof. Anil Kumar and his group in laboratory by NMR. The Ulam’s problem is a two person game in which one of the player tries to search, in minimum queries, a number thought by the other player. Classically the problem scales exponentially with the size of the number. The quantum version of the Ulam’s problem has query complexity that is independent of the dimension of the searched space. The experimental implementation of the Ulam’s problem in a three qubit system has been carried out by NMR [170].
A three player quantum “Dilemma” game deals with a situation in which each player tries to take a decision independently to maximize their individual gains. The optimal strategy in the quantum version of the game has a higher pay-off as compared to its classical counterpart. However, this advantage is lost if the initial qubits are from a noisy source. They have experimentally implemented this game by NMR and confirmed that quantum game is advantageous, till the corruption in the source qubit reaches a threshold value [166].
A programmable quantum state discriminator has been experimentally implemented using NMR on a two-qubit system, to discriminate a pair of states of the data qubit that are symmetrically located about a fixed state [155]. Both linearly and elliptically polarized states have been discriminated by suitably preparing the ancillary qubit [155].
In his another study Hadamard NMR spectroscopy has been utilized to accelerate the recording of 2D gates [165]. Using a multi-frequency pulse all the transitions of a spin system are excited according to a Hadamard matrix. The re-constructed spectra then yields a 2D spectrum in much shorter time compared to the conventional 2D spectroscopy. They have applied this idea to execute 2 and 3 qubit 2D gates, in times much shorter then the earlier method [130]. Yet in another study, experimental implementation of local adiabatic evolution algorithm has been implemented [158]. This experiment works on the principle that we start with a initial Hamiltonian whose ground state is known and is prepared into a pseudo-pure-state. The “initial” Hamiltonian in then adiabatically transported to a “final” Hamiltonian, with the ground state being adiabatically transported to the ground state of the “final” Hamiltonian. The ground state of the “final” Hamiltonian yields the “solution” state of the encoded problem A very indigenous and detailed NMR experiment has been performed for this purpose [158].
Implementation of Controlled phase shift gates and Collins version of Deutsch-Jozsa algorithm on a quadrupolar spin-7/2 nucleus using non-adiabatic geometric phases (168). Implementation of Liouville Space Search algorithm on strongly coupled spins has been carried out for the first time.(169).
Non-Destructive discrimination of Bell States by NMR using a single ancilla qubit. Following a theoretical paper by Panigrahi et al, experimental discrimination has been carried out by NMR using a single ancilla qubit with parity and phase measurements (173). Later non-destructive discrimination of arbitrary set of orthogonal quantum states has been carried out by NMR using only phase estimations (176).
(viii) Experimental Test of Quantum No-Hiding Theorem:
The quantum No-Hiding theorem says that if any physical process leads to bleaching of information from the original system, then it must reside in the rest of the universe, with no information being hidden. Prof. Anil Kumar and his group have for the first time experimentally verified the No-Hiding theorem by NMR. They demonstrated that the missing information, after the bleaching process, can be fully recovered from the ancilla qubit. This paper is published in Physical Review Letters (175).
Recent Works
edit(A). Genetic Algorithm for QIP:
Work in this area was started about 5 years ago and is continuing. They have for the first time applied Genetic Algorithm to optimize NMR experiments including those involved in Quantum Information Processing. The various applications are:
(i) Operator and State-to-State Optimization technique:, Using operator optimization we performed single qubit rotation and controlled-NOT operations. Using state to state optimization we prepared Pseudo Pure States (PPS) in a 2-qubit system and created Bell states directly from equilibrium state. This proved to be the fastest method of creation of a singlet state in a two-qubit system. The created singlet state was found to have a longer life time than the triplet state. [(PRA 86 022324 (2012)].
(iii). Quantum simulation of Dzyaloshinsky-Moriya (DM) interaction.
Quantum simulation of Dzyaloshinsky-Moriya (DM) interaction has been performed using a 2-qubit NMR system. The DM interaction is an anisotropic antisymmetric exchange interaction arising from spin-orbit coupling and is used to explain the weak ferromagnetism of antiferromagnetic crystals and is a crucial interaction in the description of many antiferromagnetic systems. Using Genetic Algorithm we have obtained a generic unitary operator decomposition to simulate the Hamiltonian DM interaction in presence of Heisenberg XY interaction. In this first study of its kind, the entanglement preservation of the relative strengths of these two interaction has been studied by NMR, which matches with the theoretical simulations. [Phys. Rev. A 89, 052331 (2014)].
(iv). Optimization of INEPT experiment for Quantitation.
A very popular and important NMR experiment (INEPT) which is used for quantitation of a mixture of compounds has been further optimized using Genetic Algorithm. Insensitive Nuclei Enhanced by Polarization Transfer (INEPT) involves transfer of magnetization for large abundant and high sensitivity proton spins to natural abundant Carbon-13 spins. However, the transfer efficiency depends on the coupling (J-coupling) between the directly bonded protons & carbons, which varies over a range of 115-170 Hz, making quantitation difficult. Signal averaging using variable delays reduces the variability of the transfer. Many people had come up sets of delays for signal averaging to reduce the variability of transfer. Using GA, we have found an optimum set of delays, which gives higher transfer with much less variation. This method is expected to be extremely useful in application of NMR to chemical quantitation. [J. Magn. Reson. 234,106 (2013)].
(B). Study of Frustration dynamics in a triangular configuration using NMR.
Prof. Anil Kumar and his group have carried out nuclear magnetic resonance experiments, which simulate the quantum transverse Ising spin system in a triangular configuration and show that quantum correlations can be used to distinguish between the frustrated and non-frustrated phases in the ground state of this system. Adiabatic state preparation methods were used to prepare the ground state of the spin system. They employed two different multipartite quantum correlation measures to analyze the experimental ground state of the system in both frustrated and non-frustrated regimes. The experimental data confirms the theoretically predicted results demonstrating that non-frustrated region shows higher quantum correlations compared to frustrated region [Phys. Rev. A 88, 022312 (2013)].
(C). Simulation of Mirror Inversion of quantum states in an XY spin chain using NMR.
They have carried out quantum simulation of unitary dynamics of an XY spin chain with pre-engineered couplings. Using this simulation they have demonstrated the mirror inversion of quantum states proposed by Albanese et al [Phys. Rev. Lett. 93, 230502 (2004)]. The experiment is performed in a 5-qubit dipolar coupled spin system using NMR. Further, using mirror inversion they also demonstrated the mirror inversion of entangled state from on end of the chain to the other end. The simulations are implemented with high fidelity.(Phys. Rev. A 90, 012306 (2014)).
Honors and awards
editFellowships of Academies
edit- Fellow of Indian Academy of Sciences, 1987
- Fellow of National Academy of Sciences, India, 1989
- Fellow of Indian National Science Academy, 1991
- Fellow of Third World Academy of Sciences, 1997.
- Fellow of International Society of Magnetic Resonance (ISMAR), 2009
Member of
edit- Council of International Conference on Magnetic Resonance in Biological Systems (ICMRBS), (1984-94). International Advisory Committee for ICMRBS - 2008.
- IUPAB Special Commission on NMR in Biology and Medicine (1994-97).
- Editorial Board of “Concepts in Magnetic Resonance” (1994-2002), John Wiley.
- Council of National Academy of Sciences, India (1997-98, 2008-09).
- Academic Committee of Raman Research Institute, Bangalore (1997-1998).
- Council of International Society of Magnetic Resonance (ISMAR) (2004 - 2013).
- Council of Indian National Science Academy (INSA) (2013-15).
- Member Editorial Board of “Resonance – Journal of Science Education” Indian Academy of Sciences, Bangalore (August 2014-July 2017).
Other Academic Recognitions
edit- “President” of the National Magnetic Resonance Society, India (2000-2003).
- “Honorary Professor” after superannuation at the Indian Institute of Science, (2003-2008).
- “Raja Ramanna Fellowship” of DAE, for 5 years (2003–2008).
- “Ramanna Fellow” of DST for three years (2008 - 2010).
- “Honorary Professor” at Centre for Bio-Medical Research (CBMR), SGPGIMS Campus, Lucknow, (2007- ).
- “Honorary Professor” at Indian Institute of Science Education and Research (IISER), Mohali, (a) for two years from Jan., 1, 2008; (b) for one year from July 2010 and (c) for 3 years from Jan 2014.
- Adjunct Professor, University of Hyderabad (2009-2012).
- National Academy of Sciences (NASI), Senior Scientist (2012- 2016).
Professional Society Membership
edit- Life Member - Indian Science Congress Association, Indian Physical Society and National Magnetic Resonance Society of India.
- Member - American Physical Society (1976- 99).
Awards
edit- Sir C.V.Raman Award for Research in Physical Sciences - UGC, 1993.
- Platinum Jubilee Lecture Award of Indian Science Congress Association, 1994.
- Chair of MSIL Professor at IISc., Bangalore (1994-97).
- Prof. K.Rangadhama Rao Memorial Lecture Award by INSA (1996).
- Federation of Indian Chambers of Commerce and Industry (FICCI) Award for “Physical Sciences including Mathematics” (1996-97).
- Alumni Award of the IISc, for “Excellence in Research in Science”, 2000.
- Goyal Prize in Chemistry (2001), from Kurukshetra University.
- DAE-Raja Ramanna Prize Lecture in Physics (2003) from JNCASR, Bangalore.
- Prof. J.C. Ghosh Memorial Award of Indian Chemical Society, Kolkata, for 2006.
- “Life-time Achievement Award” by the Indian Chemical Society for the year 2011.
- “J.C. Bose Memorial Lecture” at Indian Association for the Cultivation of Science, July 17, 2014.
Projects Funded (Recent)
edit- Study of anisotropic re-orientations in biomolecules by one and two-dimensional NMR, DAE (1997-2000). Out lay Rs. 5,63,370/-.
- Development of two-dimensional NQR Spectroscopy, DST (1998-2003).Total outlay Rs. 37,130,89/-
- Quantum Computing Using Nuclear Magnetic Resonance Techniques. DST (2004-2007). Total outlay Rs. 63,58,800/-
- Ramanna Fellowship to Prof.Anil Kumar, DST (2008-2010) Total outlay Rs. 40,20,000/-
- Centre for Quantum Information and Quantum Computing. DST (2010-2015). Total outlay 3,16,80,000/- (CQIQC- http://cts.iisc.ernet.in/CQIQC.html)