Papers by Nikhil Kotibhaskar
arXiv (Cornell University), Aug 18, 2018
Controlling the interaction graph between spins or qubits in a quantum simulator allows user-cont... more Controlling the interaction graph between spins or qubits in a quantum simulator allows user-controlled tailoring of native interactions to achieve a target Hamiltonian. The flexibility of engineering long-ranged phonon-mediated spin-spin interactions in a trapped ion quantum simulator offers such a possibility. Trapped ions, a leading candidate for simulating computationally hard quantum many-body dynamics, are most readily trapped in a linear 1D chain, limiting their utility for readily simulating higher dimensional spin models. In this work, we introduce a hybrid method of analog-digital simulation for simulating 2D spin models and dynamically changing interactions to achieve a new graph using a linear 1D chain. The method relies on time domain Hamiltonian engineering through a successive application of Stark shift gradient pulses, and wherein the pulse sequence can simply be obtained from a Fourier series decomposition of the target Hamiltonian over the space of lattice couplings. We focus on engineering 2D rectangular nearest-neighbor spin lattices, demonstrating that the required control parameters scale linearly with ion number. This hybrid approach offers compelling possibilities for the use of 1D chains in the study of Hamiltonian quenches, dynamical phase transitions, and quantum transport in 2D and 3D. We discuss a possible experimental implementation of this approach using real experimental parameters.
arXiv (Cornell University), Jun 29, 2022
Despite the progress in building sophisticated microfabricated ion traps, Paul traps employing ne... more Despite the progress in building sophisticated microfabricated ion traps, Paul traps employing needle electrodes retain their significance due to the simplicity of fabrication while producing high-quality systems suitable for quantum information processing, atomic clocks etc. For low noise operations such as minimizing 'excess micromotion', needles should be geometrically straight and aligned precisely with respect to each other. Self-terminated electrochemical etching, previously employed for fabricating ion trap needle electrodes employs a sensitive and time-consuming technique resulting in a low success rate of usable electrodes. Here we demonstrate an etching technique for quick fabrication of straight and symmetric needles with a high success rate and a simple apparatus with reduced sensitivity to alignment imperfections. The novelty of our technique comes from using a two-step approach employing turbulent etching for fast shaping and slow etching/polishing for subsequent surface finish and tip cleaning. Using this technique, needle electrodes for an ion-trap can be fabricated within a day, significantly reducing the setup time for a new apparatus. The needles fabricated via this technique have been used in our ion-trap to achieve trapping lifetimes of several months.
A segmented-blade ion trap with high optical access for quantum information processing
High quality, individual optical manipulation of ions in a trapped-ion quantum simulator
Towards a large scale fully-programmable trapped-ion quantum spin simulator
APS Division of Atomic, Molecular and Optical Physics Meeting Abstracts, 2020
Bulletin of the American Physical Society, 2019
Trapped ions, a leading candidate for quantum simulation, are most readily trapped in a linear ch... more Trapped ions, a leading candidate for quantum simulation, are most readily trapped in a linear chain, have limited ability to simulate arbitrary higher dimensional models. Here, we describe an analog and analog-digital hybrid quantum simulation protocols that leverage the phonon-mediated long range (Molmer-Sorensen) interactions between ion spins to mimic the interaction graph of 2D lattices. The traditional analog protocol requires individual control of spins and phonon modes. Here, we enhance the experimental feasibility by employingneural networks [1] to efficiently optimizethe required experimental configuration. The hybrid protocol [2], dynamically modifies the targeted interactions between all-to-all coupled spins that are feasible in current experiments. The hybrid protocol scales favorably for lattices with certain symmetries, e.g. O(N)control pulses are required to simulate a square lattice of N sites. We acknowledge financial support from U Waterloo, US ARO, NSERC Discovery grant, and TQT (CFREF). [1] Collaboration with Marina Drygala and Roger Melko [2] Rajabi et al, arXiv 1808.06124 (collaboration with Ashok Ajoy, UC Berkeley and Qudsia Quraishi, ARL).
Bulletin of the American Physical Society, 2018
Towards a large scale fully programmable trapped-ion quantum information processor
Bulletin of the American Physical Society, 2021
The trapped ions platform represents an excellent framework for Quantum information science exper... more The trapped ions platform represents an excellent framework for Quantum information science experiments. Long coherence times, extremely high state initialization and detection fidelity, inherent full-connectivity between qubits are some features that make trapped ions the ideal qubits. It is the same features that make this platform extremely suitable for quantum simulation of various physical phenomenon, particularly quantum spin models. In this thesis, I present the design and construction of an ion trapping apparatus for quantum simulation experiments. This apparatus is operational and is used for the trapping of ionized Yb atoms. The 6 electrodes of the trap, two of which are needle electrodes, are made out of tungsten. I discuss the unique technique we use to make tungsten needle electrodes. The design, construction, and testing of the Yb source, used to produce a thermal beam of Yb atoms, is also discussed. The apparatus discussed above needs to be housed inside an ultra-high...
Trapped ion is one of the leading platforms for quantum simulation experiment due to its long coh... more Trapped ion is one of the leading platforms for quantum simulation experiment due to its long coherence time and high fidelity state initialization, detection, and manipulation. To individually address ions at a single-ion level, it requires sophisticated optical engineering. In the thesis, we present a novel single qubit addressing system that is immune to imperfections of optical imaging and can scale to different size of the system. The technique is based on digital light processing with a commercially available digital micro-mirror device (DMD). A DMD is a 2D array that consists of tiny micro-mirrors that can be individually manipulated. It is commonly used in movie projectors to modulate the intensity of the light to create the desired image. However, using this technology to ions will require more sophisticated controls over optical wavefronts of the laser beams, for example, the necessity to manipulate the optical phase. It can be achieved by using the DMD as a programmable h...
Bulletin of the American Physical Society, 2018
npj Quantum Information, 2021
High-precision, individually programmable manipulation of quantum particles is crucial for scalin... more High-precision, individually programmable manipulation of quantum particles is crucial for scaling up quantum information processing (QIP) systems such as laser-cooled trapped-ions. However, restricting undesirable “crosstalk” in optical manipulation of ion qubits is fundamentally challenging due to micron-level inter-ion separation. Further, inhomogeneous ion spacing and high susceptibility to aberrations at UV wavelengths suitable for most ion-species pose severe challenges. Here, we demonstrate high-precision individual addressing (λ = 369.5 nm) of Yb+ using a reprogrammable Fourier hologram. The precision is achieved through in-situ aberration characterization via the trapped ion, and compensating (to λ/20) with the hologram. Using an iterative Fourier transformation algorithm (IFTA), we demonstrate an ultra-low (<10−4) intensity crosstalk error in creating arbitrary pair-wise addressing profiles, suitable for over fifty ions. This scheme relies on standard commercial hardwar...
arXiv: Atomic Physics, 2016
This work reports a new measurement of the hyperfine structure constant of the $\rm D_1 $ line in... more This work reports a new measurement of the hyperfine structure constant of the $\rm D_1 $ line in $ \rm ^{87}Rb $ through precision laser spectroscopy. In a departure from methods that rely on locking the laser on the transitions of interest, the technique reported here relies on scanning around the transition. This is carried out so as to overcome potential frequency shifts caused by various noise sources including electronic noise and thermal fluctuations. The value of the hyperfine constant reported here is $ A = 408.29(25) $ MHz, which is in variance from an earlier value reported from our lab but is consistent with other recent measurements.
Progress towards building a dual species programmable trapped ion quantum simulator
Bulletin of the American Physical Society, 2019
npj Quantum Information
Controlling the interaction graph between spins or qubits in a quantum simulator allows user-cont... more Controlling the interaction graph between spins or qubits in a quantum simulator allows user-controlled tailoring of native interactions to achieve a target Hamiltonian. Engineering long-ranged phonon-mediated spin-spin interactions in a trapped ion quantum simulator offers such a possibility. Trapped ions, a leading candidate for quantum simulation, are most readily trapped in a linear 1D chain, limiting their utility for readily simulating higher dimensional spin models. In this work, we introduce a hybrid method of analog-digital simulation for simulating 2D spin models which allows for the dynamic changing of interactions to achieve a new graph using a linear 1D chain. We focus this numerical work on engineering 2D rectangular nearest-neighbor spin lattices, demonstrating that the required control parameters scale linearly with ion number. This hybrid approach offers compelling possibilities for the use of 1D chains in the study of Hamiltonian quenches, dynamical phase transitions, and quantum transport in 2D and 3D.
npj Quantum Information, Apr 26, 2019
Controlling the interaction graph between spins or qubits in a quantum simulator allows user-cont... more Controlling the interaction graph between spins or qubits in a quantum simulator allows user-controlled tailoring of native interactions to achieve a target Hamiltonian. Engineering long-ranged phonon-mediated spin-spin interactions in a trapped ion quantum simulator offers such a possibility. Trapped ions, a leading candidate for quantum simulation, are most readily trapped in a linear 1D chain, limiting their utility for readily simulating higher dimensional spin models. In this work, we introduce a hybrid method of analog-digital simulation for simulating 2D spin models which allows for the dynamic changing of interactions to achieve a new graph using a linear 1D chain. We focus this numerical work on engineering 2D rectangular nearest-neighbor spin lattices, demonstrating that the required control parameters scale linearly with ion number. This hybrid approach offers compelling possibilities for the use of 1D chains in the study of Hamiltonian quenches, dynamical phase transitions, and quantum transport in 2D and 3D.
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Papers by Nikhil Kotibhaskar