Mihir Pant - Academia.edu (original) (raw)

Papers by Mihir Pant

npj Quantum Information

A central challenge for many quantum technologies concerns the generation of large entangled stat... more A central challenge for many quantum technologies concerns the generation of large entangled states of individually addressable quantum memories. Here, we show that percolation theory allows the rapid generation of arbitrarily large graph states by heralding the entanglement in a lattice of atomic memories with single-photon detection. This approach greatly reduces the time required to produce large cluster states for quantum information processing including universal one-way quantum computing. This reduction puts our architecture in an operational regime where demonstrated coupling, collection, detection efficiencies, and coherence time are sufficient. The approach also dispenses the need for time-consuming feed-forward, high cooperativity interfaces and ancilla single photons, and can tolerate a high rate of site imperfections. We derive the minimum coherence time to scalably create large cluster states, as a function of photon-collection efficiency. We also propose a variant of t...

Physical Review B

We consider the free carrier dispersion effect in a semiconductor nanocavity in the limit of disc... more We consider the free carrier dispersion effect in a semiconductor nanocavity in the limit of discrete photoexcited electron-hole pairs. This analysis reveals the possibility of ultrafast, incoherent transduction and gain from a single photon signal to a strong coherent probe field. Homodyne detection of the displaced probe field enables a new method for room temperature, photon-number-resolving single photon detection. In particular, we estimate that a single photon absorbed within a silicon nanocavity can, within tens of picoseconds, be detected with ∼99% efficiency and a dark count rate on the order of kHz assuming a mode volume V eff ∼ 10 −2 (λ/nSi) 3 for a 4.5 µm probe wavelength and a loaded quality factor Q on the order of 10 4 .

New Journal of Physics

Current proposals for scalable photonic quantum technologies require on-demand sources of indisti... more Current proposals for scalable photonic quantum technologies require on-demand sources of indistinguishable single photons with very high efficiency. Even with recent progress in the field there is still a significant gap between the requirements and state of the art performance. Here, we propose an on-chip source of time-multiplexed, heralded photons. Using quantum feedback control on a photon storage cavity with an optimized driving protocol, we estimate an on-demand efficiency of 99% and unheralded loss of order 1%, assuming high efficiency detectors and intrinsic cavity quality factors of order 10 8. We further explain how temporal-and spectral-multiplexing can be used in parallel to significantly reduce device requirements if single photon frequency conversion is possible with efficiency in the same range of 99%.

npj Quantum Information

Remote quantum entanglement can enable numerous applications including distributed quantum comput... more Remote quantum entanglement can enable numerous applications including distributed quantum computation, secure communication, and precision sensing. We consider how a quantum network-nodes equipped with limited quantum processing capabilities connected via lossy optical links-can distribute high-rate entanglement simultaneously between multiple pairs of users. We develop protocols for such quantum "repeater" nodes, which enable a pair of users to achieve large gains in entanglement rates over using a linear chain of quantum repeaters, by exploiting the diversity of multiple paths in the network. Additionally, we develop repeater protocols that enable multiple user pairs to generate entanglement simultaneously at rates that can far exceed what is possible with repeaters time sharing among assisting individual entanglement flows. Our results suggest that the early-stage development of quantum memories with short coherence times and implementations of probabilistic Bell-state measurements can have a much more profound impact on quantum networks than may be apparent from analyzing linear repeater chains. This framework should spur the development of a general quantum network theory, bringing together quantum memory physics, quantum information theory, quantum error correction, and computer network theory.

Nature Communications

Despite linear-optical fusion (Bell measurement) being probabilistic, photonic cluster states for... more Despite linear-optical fusion (Bell measurement) being probabilistic, photonic cluster states for universal quantum computation can be prepared without feed-forward by fusing small nphoton entangled clusters, if the success probability of each fusion attempt is above a threshold, λ ðnÞ c. We prove a general bound λ ðnÞ c ! 1=ðn À 1Þ, and develop a conceptual method to construct long-range-connected clusters where λ ðnÞ c becomes the bond percolation threshold of a logical graph. This mapping lets us find constructions that require lower fusion success probabilities than currently known, and settle a heretofore open question by showing that a universal cluster state can be created by fusing 3-photon clusters over a 2D lattice with a fusion success probability that is achievable with linear optics and single photons, making this attractive for integrated-photonic realizations.

Physical Review A

We present a resource-performance tradeoff of an all-optical quantum repeater that uses photon so... more We present a resource-performance tradeoff of an all-optical quantum repeater that uses photon sources, linear optics, photon detectors and classical feedforward at each repeater node, but no quantum memories. We show that the quantum-secure key rate has the form R(η) = Dη s bits per mode, where η is the end-to-end channel's transmissivity, and the constants D and s are functions of various device inefficiencies and the resource constraint, such as the number of available photon sources at each repeater node. Even with lossy devices, we show that it is possible to attain s < 1, and in turn outperform the maximum key rate attainable without quantum repeaters, R direct (η) = − log 2 (1 − η) ≈ (1/ ln 2)η bits per mode for η 1, beyond a certain total range L, where η ∼ e −αL in optical fiber. We also propose a suite of modifications to a recently-proposed alloptical repeater protocol that ours builds upon, which lower the number of photon sources required to create photonic clusters at the repeaters so as to outperform R direct (η), from ∼ 10 11 to ∼ 10 6 photon sources per repeater node. We show that the optimum separation between repeater nodes is independent of the total range L, and is around 1.5 km for assumptions we make on various device losses.

Nanophotonics, 2016

Quantum information science offers inherently more powerful methods for communication, computatio... more Quantum information science offers inherently more powerful methods for communication, computation, and precision measurement that take advantage of quantum superposition and entanglement. In recent years, theoretical and experimental advances in quantum computing and simulation with photons have spurred great interest in developing large photonic entangled states that challenge today’s classical computers. As experiments have increased in complexity, there has been an increasing need to transition bulk optics experiments to integrated photonics platforms to control more spatial modes with higher fidelity and phase stability. The silicon-on-insulator (SOI) nanophotonics platform offers new possibilities for quantum optics, including the integration of bright, nonclassical light sources, based on the large third-order nonlinearity (χHere, we discuss the SOI nanophotonics platform for quantum photonic circuits with hundreds-to-thousands of optical elements and the associated challenge...

Conference on Lasers and Electro-Optics, 2016

We present methods which allow orders of magnitude increase in the number of modes in linear opti... more We present methods which allow orders of magnitude increase in the number of modes in linear optics experiments by moving from spatial encoding to temporal encoding and using dispersion. This enables significant practical advantages for linear quantum optics and Boson Sampling experiments. Passing consecutively heralded photons through time-independent dispersion and measuring the output time of the photons is equivalent to a Boson Sampling experiment for which no efficient classical algorithm is reported, to our knowledge. With time-dependent dispersion, it is possible to implement arbitrary single-particle unitaries. Given the relatively simple requirements of these schemes, they provide a path to realizing much larger linear quantum optics experiments including post-classical Boson Sampling machines.

ABSTRACT The study of femtosecond laser induced electron emission has become important in recent ... more ABSTRACT The study of femtosecond laser induced electron emission has become important in recent years because of its application in imaging and as a femtosecond electron source. Most of the experimental studies in this area have been between the multiphoton and optical tunneling regimes where the Keldysh parameter is close to 1. Many different models have been used to describe the emission mechanism in this region including optical field emission, over-barrier emission and multiphoton emission. Here, we present a comparison of a model that combines optical field emission and multiphoton emission with pure multiphoton emission and tunneling models. A comparison of the models with experimental data including the peak-to-base ratio, energy spectrum etc. is also presented.

2010 8th International Vacuum Electron Sources Conference and Nanocarbon, 2010

ABSTRACT Shot noise is the electronic noise that occurs due to the discreteness of electronic cha... more ABSTRACT Shot noise is the electronic noise that occurs due to the discreteness of electronic charge and has a uniform frequency spectrum. The study of shot noise suppression plays an important part in studying wave-particle duality in mesoscopic devices. Quantum partitioning at high fields leads to significant electron correlation during the tunneling process. Previous models developed to study quantum shot noise suppression have been one-dimensional (1-D) with a constant field enhancement factor. In order to take into account the geometric variation of the field enhancement factor across the surface of the emitter, a two-dimensional (2-D) model is presented in this paper.

We demonstrate the generation of quantum-correlated photon pairs combined with the spectral filte... more We demonstrate the generation of quantum-correlated photon pairs combined with the spectral filtering of the pump field by more than 95 dB on a single silicon chip using electrically tunable ring resonators and passive Bragg reflectors. Moreover, we perform the demultiplexing and routing of signal and idler photons after transferring them via an optical fiber to a second identical chip. Nonclassical two-photon temporal correlations with a coincidence-to-accidental ratio of 50 are measured without further off-chip filtering. Our system, fabricated with high yield and reproducibility in a CMOS-compatible process, paves the way toward large-scale quantum photonic circuits by allowing sources and detectors of single photons to be integrated on the same chip.

ABSTRACT Ultrafast laser induced electron emission has garnered considerable interest in recent y... more ABSTRACT Ultrafast laser induced electron emission has garnered considerable interest in recent years because of its application in imaging, future light sources and in the development of ultrafast optical transistors. The photoemission process involves multiple physical processes: laser heating, quantum tunneling and acceleration by the ponderomotive force. Previous models for photoemission have only included some of these effects. In this paper, we combine the simulations of non-equilibrium heating with time-dependent quantum simulations under a spatially varying field to obtain a model which can capture all three effects. We find that many features of the emission process can only be captured by the combined model. Furthermore, the assumptions made by older models are found to be valid only under certain conditions. Our model is also compared with the classical Einstein photoelectric effect and we find differences in the emission order because of heating and the finite pulsewidth. The relative contribution of different energy levels in the emission process is also studied.

CLEO: 2014, 2014

We demonstrate an on-chip source of correlated photons with spatial demultiplexing of signal and ... more We demonstrate an on-chip source of correlated photons with spatial demultiplexing of signal and idler photons via ring resonators and with pump supression greater than 65 decibels.

Physical Review B (submitted)

Based on a time-dependent quantum model, a relation between the onset of the optical tunneling re... more Based on a time-dependent quantum model, a relation between the onset of the optical tunneling regime and the metal work function is determined. In the multiphoton regime, the number of photons required for absorption is reduced from n=3 (at pulse length τ>20 fs) to n=2 (at τ<8 fs) due to the energy uncertainty principle. The phase of the laser is important for optical tunneling, but is only manifest in the multiphoton regime when the number of laser cycles is close to or less than 1. The effect of the field gradient at the tip can be important when the radius of the tip is 40 nm or smaller. The extension of the model to include nonequilibrium electron distribution due to ultrafast laser excitation is discussed. Comparisons with other models and experimental findings are presented.

Journal of Applied Physics, Jan 1, 2010

This paper presents a two-dimensional nonuniform model to calculate the quantum shot noise suppre... more This paper presents a two-dimensional nonuniform model to calculate the quantum shot noise suppression (or Fano factor) for electron field emission from a single field emitter of two different shapes: Lorentzian and prolate spheroidal. Between them, the Lorentzian field emitter has a larger shot noise suppression. For a given sharp emitter at a fixed work function, there is a minimum value of the Fano factor, which is independent of the geometrical sharpness of the emitter, and it increases with larger work function. Comparison with the one-dimensional uniform model has implied that prior results had overestimated the shot noise suppression.

npj Quantum Information

A central challenge for many quantum technologies concerns the generation of large entangled stat... more A central challenge for many quantum technologies concerns the generation of large entangled states of individually addressable quantum memories. Here, we show that percolation theory allows the rapid generation of arbitrarily large graph states by heralding the entanglement in a lattice of atomic memories with single-photon detection. This approach greatly reduces the time required to produce large cluster states for quantum information processing including universal one-way quantum computing. This reduction puts our architecture in an operational regime where demonstrated coupling, collection, detection efficiencies, and coherence time are sufficient. The approach also dispenses the need for time-consuming feed-forward, high cooperativity interfaces and ancilla single photons, and can tolerate a high rate of site imperfections. We derive the minimum coherence time to scalably create large cluster states, as a function of photon-collection efficiency. We also propose a variant of t...

Physical Review B

We consider the free carrier dispersion effect in a semiconductor nanocavity in the limit of disc... more We consider the free carrier dispersion effect in a semiconductor nanocavity in the limit of discrete photoexcited electron-hole pairs. This analysis reveals the possibility of ultrafast, incoherent transduction and gain from a single photon signal to a strong coherent probe field. Homodyne detection of the displaced probe field enables a new method for room temperature, photon-number-resolving single photon detection. In particular, we estimate that a single photon absorbed within a silicon nanocavity can, within tens of picoseconds, be detected with ∼99% efficiency and a dark count rate on the order of kHz assuming a mode volume V eff ∼ 10 −2 (λ/nSi) 3 for a 4.5 µm probe wavelength and a loaded quality factor Q on the order of 10 4 .

New Journal of Physics

Current proposals for scalable photonic quantum technologies require on-demand sources of indisti... more Current proposals for scalable photonic quantum technologies require on-demand sources of indistinguishable single photons with very high efficiency. Even with recent progress in the field there is still a significant gap between the requirements and state of the art performance. Here, we propose an on-chip source of time-multiplexed, heralded photons. Using quantum feedback control on a photon storage cavity with an optimized driving protocol, we estimate an on-demand efficiency of 99% and unheralded loss of order 1%, assuming high efficiency detectors and intrinsic cavity quality factors of order 10 8. We further explain how temporal-and spectral-multiplexing can be used in parallel to significantly reduce device requirements if single photon frequency conversion is possible with efficiency in the same range of 99%.

npj Quantum Information

Remote quantum entanglement can enable numerous applications including distributed quantum comput... more Remote quantum entanglement can enable numerous applications including distributed quantum computation, secure communication, and precision sensing. We consider how a quantum network-nodes equipped with limited quantum processing capabilities connected via lossy optical links-can distribute high-rate entanglement simultaneously between multiple pairs of users. We develop protocols for such quantum "repeater" nodes, which enable a pair of users to achieve large gains in entanglement rates over using a linear chain of quantum repeaters, by exploiting the diversity of multiple paths in the network. Additionally, we develop repeater protocols that enable multiple user pairs to generate entanglement simultaneously at rates that can far exceed what is possible with repeaters time sharing among assisting individual entanglement flows. Our results suggest that the early-stage development of quantum memories with short coherence times and implementations of probabilistic Bell-state measurements can have a much more profound impact on quantum networks than may be apparent from analyzing linear repeater chains. This framework should spur the development of a general quantum network theory, bringing together quantum memory physics, quantum information theory, quantum error correction, and computer network theory.

Nature Communications

Despite linear-optical fusion (Bell measurement) being probabilistic, photonic cluster states for... more Despite linear-optical fusion (Bell measurement) being probabilistic, photonic cluster states for universal quantum computation can be prepared without feed-forward by fusing small nphoton entangled clusters, if the success probability of each fusion attempt is above a threshold, λ ðnÞ c. We prove a general bound λ ðnÞ c ! 1=ðn À 1Þ, and develop a conceptual method to construct long-range-connected clusters where λ ðnÞ c becomes the bond percolation threshold of a logical graph. This mapping lets us find constructions that require lower fusion success probabilities than currently known, and settle a heretofore open question by showing that a universal cluster state can be created by fusing 3-photon clusters over a 2D lattice with a fusion success probability that is achievable with linear optics and single photons, making this attractive for integrated-photonic realizations.

Physical Review A

We present a resource-performance tradeoff of an all-optical quantum repeater that uses photon so... more We present a resource-performance tradeoff of an all-optical quantum repeater that uses photon sources, linear optics, photon detectors and classical feedforward at each repeater node, but no quantum memories. We show that the quantum-secure key rate has the form R(η) = Dη s bits per mode, where η is the end-to-end channel's transmissivity, and the constants D and s are functions of various device inefficiencies and the resource constraint, such as the number of available photon sources at each repeater node. Even with lossy devices, we show that it is possible to attain s < 1, and in turn outperform the maximum key rate attainable without quantum repeaters, R direct (η) = − log 2 (1 − η) ≈ (1/ ln 2)η bits per mode for η 1, beyond a certain total range L, where η ∼ e −αL in optical fiber. We also propose a suite of modifications to a recently-proposed alloptical repeater protocol that ours builds upon, which lower the number of photon sources required to create photonic clusters at the repeaters so as to outperform R direct (η), from ∼ 10 11 to ∼ 10 6 photon sources per repeater node. We show that the optimum separation between repeater nodes is independent of the total range L, and is around 1.5 km for assumptions we make on various device losses.

Nanophotonics, 2016

Quantum information science offers inherently more powerful methods for communication, computatio... more Quantum information science offers inherently more powerful methods for communication, computation, and precision measurement that take advantage of quantum superposition and entanglement. In recent years, theoretical and experimental advances in quantum computing and simulation with photons have spurred great interest in developing large photonic entangled states that challenge today’s classical computers. As experiments have increased in complexity, there has been an increasing need to transition bulk optics experiments to integrated photonics platforms to control more spatial modes with higher fidelity and phase stability. The silicon-on-insulator (SOI) nanophotonics platform offers new possibilities for quantum optics, including the integration of bright, nonclassical light sources, based on the large third-order nonlinearity (χHere, we discuss the SOI nanophotonics platform for quantum photonic circuits with hundreds-to-thousands of optical elements and the associated challenge...

Conference on Lasers and Electro-Optics, 2016

We present methods which allow orders of magnitude increase in the number of modes in linear opti... more We present methods which allow orders of magnitude increase in the number of modes in linear optics experiments by moving from spatial encoding to temporal encoding and using dispersion. This enables significant practical advantages for linear quantum optics and Boson Sampling experiments. Passing consecutively heralded photons through time-independent dispersion and measuring the output time of the photons is equivalent to a Boson Sampling experiment for which no efficient classical algorithm is reported, to our knowledge. With time-dependent dispersion, it is possible to implement arbitrary single-particle unitaries. Given the relatively simple requirements of these schemes, they provide a path to realizing much larger linear quantum optics experiments including post-classical Boson Sampling machines.

ABSTRACT The study of femtosecond laser induced electron emission has become important in recent ... more ABSTRACT The study of femtosecond laser induced electron emission has become important in recent years because of its application in imaging and as a femtosecond electron source. Most of the experimental studies in this area have been between the multiphoton and optical tunneling regimes where the Keldysh parameter is close to 1. Many different models have been used to describe the emission mechanism in this region including optical field emission, over-barrier emission and multiphoton emission. Here, we present a comparison of a model that combines optical field emission and multiphoton emission with pure multiphoton emission and tunneling models. A comparison of the models with experimental data including the peak-to-base ratio, energy spectrum etc. is also presented.

2010 8th International Vacuum Electron Sources Conference and Nanocarbon, 2010

ABSTRACT Shot noise is the electronic noise that occurs due to the discreteness of electronic cha... more ABSTRACT Shot noise is the electronic noise that occurs due to the discreteness of electronic charge and has a uniform frequency spectrum. The study of shot noise suppression plays an important part in studying wave-particle duality in mesoscopic devices. Quantum partitioning at high fields leads to significant electron correlation during the tunneling process. Previous models developed to study quantum shot noise suppression have been one-dimensional (1-D) with a constant field enhancement factor. In order to take into account the geometric variation of the field enhancement factor across the surface of the emitter, a two-dimensional (2-D) model is presented in this paper.

We demonstrate the generation of quantum-correlated photon pairs combined with the spectral filte... more We demonstrate the generation of quantum-correlated photon pairs combined with the spectral filtering of the pump field by more than 95 dB on a single silicon chip using electrically tunable ring resonators and passive Bragg reflectors. Moreover, we perform the demultiplexing and routing of signal and idler photons after transferring them via an optical fiber to a second identical chip. Nonclassical two-photon temporal correlations with a coincidence-to-accidental ratio of 50 are measured without further off-chip filtering. Our system, fabricated with high yield and reproducibility in a CMOS-compatible process, paves the way toward large-scale quantum photonic circuits by allowing sources and detectors of single photons to be integrated on the same chip.

ABSTRACT Ultrafast laser induced electron emission has garnered considerable interest in recent y... more ABSTRACT Ultrafast laser induced electron emission has garnered considerable interest in recent years because of its application in imaging, future light sources and in the development of ultrafast optical transistors. The photoemission process involves multiple physical processes: laser heating, quantum tunneling and acceleration by the ponderomotive force. Previous models for photoemission have only included some of these effects. In this paper, we combine the simulations of non-equilibrium heating with time-dependent quantum simulations under a spatially varying field to obtain a model which can capture all three effects. We find that many features of the emission process can only be captured by the combined model. Furthermore, the assumptions made by older models are found to be valid only under certain conditions. Our model is also compared with the classical Einstein photoelectric effect and we find differences in the emission order because of heating and the finite pulsewidth. The relative contribution of different energy levels in the emission process is also studied.

CLEO: 2014, 2014

We demonstrate an on-chip source of correlated photons with spatial demultiplexing of signal and ... more We demonstrate an on-chip source of correlated photons with spatial demultiplexing of signal and idler photons via ring resonators and with pump supression greater than 65 decibels.

Physical Review B (submitted)

Based on a time-dependent quantum model, a relation between the onset of the optical tunneling re... more Based on a time-dependent quantum model, a relation between the onset of the optical tunneling regime and the metal work function is determined. In the multiphoton regime, the number of photons required for absorption is reduced from n=3 (at pulse length τ>20 fs) to n=2 (at τ<8 fs) due to the energy uncertainty principle. The phase of the laser is important for optical tunneling, but is only manifest in the multiphoton regime when the number of laser cycles is close to or less than 1. The effect of the field gradient at the tip can be important when the radius of the tip is 40 nm or smaller. The extension of the model to include nonequilibrium electron distribution due to ultrafast laser excitation is discussed. Comparisons with other models and experimental findings are presented.

Journal of Applied Physics, Jan 1, 2010

This paper presents a two-dimensional nonuniform model to calculate the quantum shot noise suppre... more This paper presents a two-dimensional nonuniform model to calculate the quantum shot noise suppression (or Fano factor) for electron field emission from a single field emitter of two different shapes: Lorentzian and prolate spheroidal. Between them, the Lorentzian field emitter has a larger shot noise suppression. For a given sharp emitter at a fixed work function, there is a minimum value of the Fano factor, which is independent of the geometrical sharpness of the emitter, and it increases with larger work function. Comparison with the one-dimensional uniform model has implied that prior results had overestimated the shot noise suppression.