@article{farfurnik_singh_luo_bracker_carter_pettit_waks_2023, title={All-Optical Noise Spectroscopy of a Solid-State Spin}, volume={23}, ISSN={1530-6984 1530-6992}, url={http://dx.doi.org/10.1021/acs.nanolett.2c04552}, DOI={10.1021/acs.nanolett.2c04552}, abstractNote={Noise spectroscopy elucidates the fundamental noise sources in spin systems, thereby serving as an essential tool toward developing spin qubits with long coherence times for quantum information processing, communication, and sensing. But existing techniques for noise spectroscopy that rely on microwave fields become infeasible when the microwave power is too weak to generate Rabi rotations of the spin. Here, we demonstrate an alternative all-optical approach to performing noise spectroscopy. Our approach utilizes coherent Raman rotations of the spin state with controlled timing and phase to implement Carr-Purcell-Meiboom-Gill pulse sequences. Analyzing the spin dynamics under these sequences enables us to extract the noise spectrum of a dense ensemble of nuclear spins interacting with a single spin in a quantum dot, which has thus far been modeled only theoretically. By providing spectral bandwidths of over 100 MHz, our approach enables studies of spin dynamics and decoherence for a broad range of solid-state spin qubits.}, number={5}, journal={Nano Letters}, publisher={American Chemical Society (ACS)}, author={Farfurnik, Demitry and Singh, Harjot and Luo, Zhouchen and Bracker, Allan S. and Carter, Samuel G. and Pettit, Robert M. and Waks, Edo}, year={2023}, month={Feb}, pages={1781–1786} }
 @article{dutta_zhao_saha_farfurnik_goldschmidt_waks_2023, title={An Atomic Frequency Comb Memory in Rare-Earth-Doped Thin-Film Lithium Niobate}, volume={3}, ISSN={2330-4022 2330-4022}, url={http://dx.doi.org/10.1021/acsphotonics.2c01835}, DOI={10.1021/acsphotonics.2c01835}, abstractNote={Quantum memories are a key building block for optical quantum computers and quantum networks. Rare-earth ion-doped crystals are a promising material to achieve quantum memory using an atomic frequency comb protocol. However, current atomic frequency comb memories typically use bulk materials or waveguides with large cross sections or rely on fabrication techniques not easily adaptable to wafer scale processing. Here, we demonstrate a compact chip-integrated atomic frequency comb in rare-earth-doped thin-film lithium niobate. Our optical memory exhibits a broad storage bandwidth exceeding 100 MHz and optical storage time as long as 250 ns. The enhanced optical confinement in this device leads to three orders of magnitude reduction in optical power required for a coherent control as compared to ion-diffused waveguides. These compact atomic frequency comb memories pave the way toward scalable, highly efficient, electro-optically tunable quantum photonic systems that can store and manipulate light on a compact chip.}, journal={ACS Photonics}, publisher={American Chemical Society (ACS)}, author={Dutta, Subhojit and Zhao, Yuqi and Saha, Uday and Farfurnik, Demitry and Goldschmidt, Elizabeth A. and Waks, Edo}, year={2023}, month={Mar} }
 @article{huang_farfurnik_seif_hafezi_liu_2023, title={Random Pulse Sequences for Qubit Noise Spectroscopy}, url={https://arxiv.org/abs/2303.00909}, DOI={10.48550/ARXIV.2303.00909}, abstractNote={Qubit noise spectroscopy is an important tool for the experimental investigation of open quantum systems. However, conventional techniques for implementing noise spectroscopy are time-consuming, because they require multiple measurements of the noise spectral density at different frequencies. Here we describe an alternative method for quickly characterizing the spectral density. Our method utilizes random pulse sequences, with carefully-controlled correlations among the pulses, to measure arbitrary linear functionals of the noise spectrum. Such measurements allow us to estimate $k$'th-order moments of the noise spectrum, as well as to reconstruct sparse noise spectra via compressed sensing. Our simulations of the performance of the random pulse sequences on a realistic physical system, self-assembled quantum dots, reveal a speedup of an order of magnitude in extracting the noise spectrum compared to conventional dynamical decoupling approaches.}, publisher={arXiv}, author={Huang, Kaixin and Farfurnik, Demitry and Seif, Alireza and Hafezi, Mohammad and Liu, Yi-Kai}, year={2023} }
 @inproceedings{farfurnik_2022, title={All-optical Raman-based noise spectroscopy of a solid-state spin}, booktitle={APS March Meeting}, author={Farfurnik, D.}, year={2022}, month={Mar} }
 @article{singh_farfurnik_luo_bracker_carter_waks_2022, title={Optical Transparency Induced by a Largely Purcell Enhanced Quantum Dot in a Polarization-Degenerate Cavity}, volume={22}, ISSN={1530-6984 1530-6992}, url={http://dx.doi.org/10.1021/acs.nanolett.2c03098}, DOI={10.1021/acs.nanolett.2c03098}, abstractNote={Optically active spin systems coupled to photonic cavities with high cooperativity can generate strong light-matter interactions, a key ingredient in quantum networks. However, obtaining high cooperativities for quantum information processing often involves the use of photonic crystal cavities that feature a poor optical access from the free space, especially to circularly polarized light required for the coherent control of the spin. Here, we demonstrate coupling with a cooperativity as high as 8 of an InAs/GaAs quantum dot to a fabricated bullseye cavity that provides nearly degenerate and Gaussian polarization modes for efficient optical accessing. We observe spontaneous emission lifetimes of the quantum dot as short as 80 ps (an ∼15 Purcell enhancement) and a ∼80% transparency of light reflected from the cavity. Leveraging the induced transparency for photon switching while coherently controlling the quantum dot spin could contribute to ongoing efforts of establishing quantum networks.}, number={19}, journal={Nano Letters}, publisher={American Chemical Society (ACS)}, author={Singh, Harjot and Farfurnik, Demitry and Luo, Zhouchen and Bracker, Allan S. and Carter, Samuel G. and Waks, Edo}, year={2022}, month={Sep}, pages={7959–7964} }
 @inproceedings{farfurnik_2022, title={Optical transparency induced by a largely Purcell-enhanced single photon emitter in a low-Q cavity}, booktitle={SPIE Optics and Photonics Conference}, author={Farfurnik, D.}, year={2022}, month={Aug} }
 @inproceedings{farfurnik_singh_luo_bracker_carter_pettit_waks_2021, title={All-optical Raman-based noise spectroscopy of solid-state spin qubits}, url={http://dx.doi.org/10.1364/qim.2021.m2b.3}, DOI={10.1364/qim.2021.m2b.3}, abstractNote={We introduce an all-optical approach for noise spectroscopy of solid-state spin qubits, based on Raman control and the Carr-Purcell-Meiboom-Gill pulse sequences, and use it to extract the noise spectra of self-assembled quantum dots.}, booktitle={Quantum Information and Measurement VI 2021}, publisher={Optica Publishing Group}, author={Farfurnik, Demitry and Singh, Harjot and Luo, Zhouchen and Bracker, Allan S. and Carter, Samuel G. and Pettit, Robert M. and Waks, Edo}, year={2021} }
 @article{farfurnik_pettit_luo_waks_2021, title={Single-Shot Readout of a Solid-State Spin in a Decoherence-Free Subspace}, volume={15}, url={https://doi.org/10.1103/PhysRevApplied.15.L031002}, DOI={10.1103/PhysRevApplied.15.L031002}, abstractNote={The efficient single photon emission capabilities of quantum dot molecules position them as promising platforms for quantum information processing. Furthermore, quantum dot molecules feature a "decoherence-free" subspace that enables spin qubits with long coherence time. To efficiently read out the spin state within this subspace requires optically cycling isolated transitions that originate from a triplet manifold within the quantum dot molecule. We propose and theoretically study a two-stage spin readout protocol within this decoherence-free subspace that allows single-shot readout performance. The process incorporates a microwave $\pi$-pulse and optically cycling the isolated transitions, which induces fluorescence that allows us to identify the initial spin state. This protocol offers enhanced readout fidelity compared to previous schemes that rely on the excitation of transitions that strongly decay to multiple ground states or require long initialization via slow, optically forbidden transitions. By simulating the performance of the protocol, we show that an optimal spin readout fidelity of over 97% and single-shot readout performance are achievable for a photon collection efficiency of just 0.12%. This high readout performance for such realistic photon collection conditions within the decoherence-free subspace expands the potential of quantum dot molecules as building blocks for quantum networks.}, number={3}, journal={Physical Review Applied}, publisher={American Physical Society (APS)}, author={Farfurnik, D. and Pettit, R. M. and Luo, Z. and Waks, E.}, year={2021}, month={Mar} }
 @inproceedings{farfurnik_pettit_luo_ravan_waks_2020, title={Arbitrary sequenced spin control of a Quantum Dot strongly coupled to a photonic crystal cavity}, url={http://dx.doi.org/10.1364/fio.2020.fw4c.5}, DOI={10.1364/fio.2020.fw4c.5}, abstractNote={We study the spin dynamics of Quantum Dots under an optical field modulated at the full operation range of a temperature-stabilized electro optical modulator, and spin manipulation capabilities for dots strongly coupled to L3 cavities.}, booktitle={Frontiers in Optics / Laser Science}, publisher={Optica Publishing Group}, author={Farfurnik, Demitry and Pettit, Robert M. and Luo, Zhouchen and Ravan, Shantam M. and Waks, Edo}, year={2020} }
 @article{farfurnik_bar-gill_2020, title={Characterizing spin-bath parameters using conventional and time-asymmetric Hahn-echo sequences}, volume={101}, url={https://doi.org/10.1103/PhysRevB.101.104306}, DOI={10.1103/PhysRevB.101.104306}, abstractNote={Spin-bath noise characterization, which is typically performed by multi-pulse control sequences, is essential for understanding most spin dynamics in the solid-state. Here, we theoretically propose a method for extracting the characteristic parameters of a noise source with a known spectrum, using a single modified Hahn-Echo sequence. By varying the application time of the pulse, measuring the coherence curves of an addressable spin, and fitting the decay coefficients to a theoretical function derived by us, we extract parameters characterizing the physical nature of the noise. Assuming a Lorentzian noise spectrum, we illustrate this method for extracting the correlation time of a bath of nitrogen paramagnetic impurities in diamond, and its coupling strength to the addressable spin of a Nitrogen-Vacancy center. Considering a realistic experimental scenario with $5\%$ readout error, the parameters can be extracted with an accuracy of $\sim 10 \%$. The scheme is effective for samples having a natural homogeneous coherence time ($T_2$) up to two orders of magnitude greater than the inhomogeneous coherence time ($T_2^*$). Beyond its potential for reducing experiment times by an order-of-magnitude, such single-pulse noise characterization could minimize the effects of long time-scale technical noise and accumulating pulse imperfections.}, number={10}, journal={Physical Review B}, publisher={American Physical Society (APS)}, author={Farfurnik, D. and Bar-Gill, N.}, year={2020}, month={Mar} }
 @article{farfurnik_bar-gill_2020, title={Hamiltonian engineering of general two-body spin-1/2 interactions}, volume={2}, url={https://doi.org/10.1103/PhysRevResearch.2.013061}, DOI={10.1103/PhysRevResearch.2.013061}, abstractNote={Spin Hamiltonian engineering in solid-state systems plays a key role in a variety of applications ranging from quantum information processing and quantum simulations to novel studies of many-body physics. By analyzing the irreducible form of a general two-body spin-1/2 Hamiltonian, we identify all interchangeable interaction terms using rotation pulses. Based on this identification, we derive novel pulse sequences, defined by an icosahedral symmetry group, providing the most general achievable manipulation of interaction terms. We demonstrate that, compared to conventional Clifford rotations, these sequences offer advantages for creating Zeeman terms essential for magnetic sensing, and could be utilized to generate new interaction forms. The exact series of pulses required to generate desired interaction terms can be determined from a linear programming algorithm. For realizing the sequences, we propose two experimental approaches, involving pulse product de-composition, and off-resonant driving. Resulting engineered Hamiltonians could contribute to the understanding of many-body physics, and result in the creation of novel quantum simulators and the generation of highly-entangled states, thereby opening avenues in quantum sensing and information processing.}, number={1}, journal={Physical Review Research}, publisher={American Physical Society (APS)}, author={Farfurnik, D. and Bar-Gill, N.}, year={2020}, month={Jan} }
 @inproceedings{farfurnik_2020, title={Single-shot readout of a solid-state spin in a decoherence-free subspace}, booktitle={11th International Conference On Quantum Dots}, author={Farfurnik, D.}, year={2020}, month={Dec} }
 @inproceedings{farfurnik_bar-gill_2019, title={Spin ensembles in diamond for sensing and many-body physics}, url={http://dx.doi.org/10.1364/qim.2019.f3b.2}, DOI={10.1364/qim.2019.f3b.2}, abstractNote={In this work, we enhance the coherence properties and spin concentrations of ensembles of Nitrogen-Vacancy centers in diamond towards efficient magnetic sensing and the studies of many-body dipolar dynamics}, booktitle={Quantum Information and Measurement (QIM) V: Quantum Technologies}, publisher={OSA}, author={Farfurnik, Demitry and Bar-Gill, Nir}, year={2019} }
 @article{dziewior_knips_farfurnik_senkalla_benshalom_efroni_meinecke_bar-ad_weinfurter_vaidman_2019, title={Universality of local weak interactions and its application for interferometric alignment}, volume={116}, DOI={10.1073/pnas.1812970116}, abstractNote={The modification of the effect of interactions of a particle as a function of its preselected and postselected states is analyzed theoretically and experimentally. The universality property of this modification in the case of local interactions of a spatially preselected and postselected particle has been found. It allowed us to define an operational approach for the characterization of the presence of a quantum particle in a particular place: the way it modifies the effect of local interactions. The experiment demonstrating this universality property provides an efficient interferometric alignment method, in which the position of the beam on a single detector throughout one phase scan yields all misalignment parameters.}, number={8}, journal={Proceedings of the National Academy of Sciences}, publisher={Proceedings of the National Academy of Sciences}, author={Dziewior, Jan and Knips, Lukas and Farfurnik, Demitry and Senkalla, Katharina and Benshalom, Nimrod and Efroni, Jonathan and Meinecke, Jasmin and Bar-Ad, Shimshon and Weinfurter, Harald and Vaidman, Lev}, year={2019}, month={Feb}, pages={2881–2890} }
 @article{alfasi_masis_winik_farfurnik_shtempluck_bar-gill_buks_2018, title={Exploring the nonlinear regime of light-matter interaction using electronic spins in diamond}, volume={97}, DOI={10.1103/physreva.97.063808}, abstractNote={The coupling between defects in diamond and a superconducting microwave resonator is studied in the nonlinear regime. Both negatively charged nitrogen-vacancy and P1 defects are explored. The measured cavity mode response exhibits strong nonlinearity near a spin resonance. Data is compared with theoretical predictions and a good agreement is obtained in a wide range of externally controlled parameters. The nonlinear effect under study in the current paper is expected to play a role in any cavity-based magnetic resonance imaging technique and to impose a fundamental limit upon its sensitivity.}, number={6}, journal={Physical Review A}, publisher={American Physical Society (APS)}, author={Alfasi, Nir and Masis, Sergei and Winik, Roni and Farfurnik, Demitry and Shtempluck, Oleg and Bar-Gill, Nir and Buks, Eyal}, year={2018}, month={Jun} }
 @article{farfurnik_horowicz_bar-gill_2018, title={Identifying and decoupling many-body interactions in spin ensembles in diamond}, volume={98}, DOI={10.1103/physreva.98.033409}, abstractNote={In this work, we simualte the dynamics of varying density spin-ensembles in typical solid-state systems such as the Nitrogen-Vacancy (NV) centers in diamond. We propose an efficient method for simulating the averaged dynamics of large ensembles (> 1000) of spins, and consider the effects of various control sequences on the dynamics, under a realistic "spin-bath" environment. We reveal that spin-locking is efficient for decoupling spin initialized along the driving axis from their internal dipolar interactions, as well as from the external spin-bath environment, when the driving is two orders of magnitude stronger than these interactions. Since the application of standard pulsed dynamical decoupling (DD) sequences lead to strong decoupling from the environment, while the WAHUHA sequence leads to the decoupling of internal dipolar interactions, these sequences can be used for distinguishing between these two types of interactions. Moreover, the combined application of WAHUHA with standard pulsed DD could lead to decouple both interaction types, which can lead to the preservation of arbitrary states of the ensemble, and allow additional spin manipulations. By considering the effects of DD protocols with realistic finite pulses, we show that the decoupling efficiency of a standard protocol improves with the pulse durations, due to the spin-bath - microwave control interplay within the pulse durations.}, number={3}, journal={Physical Review A}, publisher={American Physical Society (APS)}, author={Farfurnik, D. and Horowicz, Y. and Bar-Gill, N.}, year={2018}, month={Sep} }
 @article{farfurnik_jarmola_budker_bar-gill_2018, title={Spin ensemble-based AC magnetometry using concatenated dynamical decoupling at low temperatures}, volume={20}, ISSN={2040-8978 2040-8986}, url={http://dx.doi.org/10.1088/2040-8986/aaa1bf}, DOI={10.1088/2040-8986/aaa1bf}, abstractNote={Ensembles of nitrogen-vacancy centers in diamond are widely used as AC magnetometers. While such measurements are usually performed using standard (XY) dynamical decoupling (DD) protocols at room temperature, we study the sensitivities achieved by utilizing various DD protocols, for measuring magnetic AC fields at frequencies in the 10–250 kHz range, at room temperature and 77 K. By performing measurements on an isotopically pure 12C sample, we find that the Carr-Purcell–Meiboom-Gill protocol, which is not robust against pulse imperfections, is less efficient for magnetometry than robust XY-based sequences. The concatenation of a standard XY-based protocol may enhance the sensitivities only for measuring high-frequency fields, for which many ( > 500 ) DD pulses are necessary and the robustness against pulse imperfections is critical. Moreover, we show that cooling is effective only for measuring low-frequency fields (∼10 kHz), for which the experiment time approaches T1 at a small number of applied DD pulses.}, number={2}, journal={Journal of Optics}, publisher={IOP Publishing}, author={Farfurnik, D and Jarmola, A and Budker, D and Bar-Gill, N}, year={2018}, month={Jan}, pages={024008} }
 @inproceedings{farfurnik_2018, title={Spin ensembles in diamond for sensing and many-body Physics}, booktitle={Center of Quantum Information Science & Technology conference}, author={Farfurnik, D.}, year={2018}, month={May} }
 @article{farfurnik_alfasi_masis_kauffmann_farchi_romach_hovav_buks_bar-gill_2017, title={Enhanced concentrations of nitrogen-vacancy centers in diamond through TEM irradiation}, volume={111}, ISSN={0003-6951 1077-3118}, url={http://dx.doi.org/10.1063/1.4993257}, DOI={10.1063/1.4993257}, abstractNote={The studies of many-body dynamics of interacting spin ensembles, as well as quantum sensing in solid state systems, are often limited by the need for high spin concentrations, along with efficient decoupling of the spin ensemble from its environment. In particular, for an ensemble of nitrogen-vacancy (NV) centers in diamond, high conversion efficiencies between nitrogen (P1) defects and NV centers are essential while maintaining long coherence times of an NV ensemble. In this work, we study the effect of electron irradiation on the conversion efficiency and the coherence time of various types of diamond samples with different initial nitrogen concentrations. The samples were irradiated using a 200 keV transmission electron microscope. Our study reveals that the efficiency of NV creation strongly depends on the initial conversion efficiency and on the initial nitrogen concentration. The irradiation of the examined samples exhibits an order of magnitude improvement in the NV concentration (up to ∼1011 NV/cm2), without degradation in their coherence time of ∼180 μs. We address the potential of this technique toward the study of many-body physics of NV ensembles and the creation of non-classical spin states for quantum sensing.}, number={12}, journal={Applied Physics Letters}, publisher={AIP Publishing}, author={Farfurnik, D. and Alfasi, N. and Masis, S. and Kauffmann, Y. and Farchi, E. and Romach, Y. and Hovav, Y. and Buks, E. and Bar-Gill, N.}, year={2017}, month={Sep} }
 @inproceedings{farfurnik_2017, title={Enhanced nitrogen-vacancy concentration in diamond through optimized electron irradiation}, booktitle={OASIS6 Conference on Optics and Electro-Optics}, author={Farfurnik, D.}, year={2017}, month={Feb} }
 @article{farfurnik_aharon_cohen_hovav_retzker_bar-gill_2017, title={Experimental realization of time-dependent phase-modulated continuous dynamical decoupling}, volume={96}, DOI={10.1103/physreva.96.013850}, abstractNote={The coherence times achieved with continuous dynamical decoupling techniques are often limited by fluctuations in the driving amplitude. In this work, we use time-dependent phase-modulated continuous driving to increase the robustness against such fluctuations in a dense ensemble of nitrogen-vacancy centers in diamond. Considering realistic experimental errors in the system, we identify the optimal modulation strength, and demonstrate an improvement of an order of magnitude in the spin-preservation of arbitrary states over conventional single continuous driving. The phase-modulated driving exhibits comparable results to previously examined amplitude-modulated techniques, and is expected to outperform them in experimental systems having higher phase accuracy. The proposed technique could open new avenues for quantum information processing and many body physics, in systems dominated by high frequency spin-bath noise, for which pulsed dynamical decoupling is less effective.}, number={1}, journal={Physical Review A}, publisher={American Physical Society (APS)}, author={Farfurnik, D. and Aharon, N. and Cohen, I. and Hovav, Y. and Retzker, A. and Bar-Gill, N.}, year={2017}, month={Jul} }
 @inproceedings{farfurnik_2017, title={Identifying and decoupling many-body interactions in spin ensembles in diamond}, booktitle={The Israel Physical Society Annual Meeting, Technion}, author={Farfurnik, D.}, year={2017}, month={Dec} }
 @article{farchi_ebert_farfurnik_haim_shaar_bar-gill_2017, title={Quantitative Vectorial Magnetic Imaging of Multi-Domain Rock Forming Minerals Using Nitrogen-Vacancy Centers in Diamond}, volume={07}, DOI={10.1142/s201032471740015x}, abstractNote={Magnetization in rock samples is crucial for paleomagnetometry research, as it harbors valuable geological information on long term processes, such as tectonic movements and the formation of oceans and continents. Nevertheless, current techniques are limited in their ability to measure high spatial resolution and high-sensitivity quantitative vectorial magnetic signatures from individual minerals and micrometer scale samples. As a result, our understanding of bulk rock magnetization is limited, specifically for the case of multi-domain minerals. In this work, we use a newly developed nitrogen-vacancy magnetic microscope, capable of quantitative vectorial magnetic imaging with optical resolution. We demonstrate direct imaging of the vectorial magnetic field of a single, multi-domain dendritic magnetite, as well as the measurement and calculation of the weak magnetic moments of an individual grain on the micron scale. These results pave the way for future applications in paleomagnetometry and for the fundamental understanding of magnetization in multi-domain samples.}, number={03}, journal={SPIN}, publisher={World Scientific Pub Co Pte Lt}, author={Farchi, E. and Ebert, Y. and Farfurnik, D. and Haim, G. and Shaar, R. and Bar-Gill, N.}, year={2017}, month={Oct}, pages={1740015} }
 @inproceedings{farfurnik_2016, title={Enhanced nitrogen-vacancy concentration in diamond through optimized electron irradiation}, booktitle={The Israel Physical Society Annual Meeting}, author={Farfurnik, D.}, year={2016}, month={Dec} }
 @inproceedings{farfurnik_jarmola_pham_wang_dobrovitski_walsworth_budker_bar-gill_2016, title={Improving the coherence properties of solid-state spin ensembles via optimized dynamical decoupling}, ISSN={0277-786X}, url={http://dx.doi.org/10.1117/12.2227479}, DOI={10.1117/12.2227479}, abstractNote={In this work, we optimize a dynamical decoupling (DD) protocol to improve the spin coherence properties of a dense ensemble of nitrogen-vacancy (NV) centers in diamond. Using liquid nitrogen-based cooling and DD microwave pulses, we increase the transverse coherence time T2 from ∼ 0.7 ms up to ∼ 30 ms. We extend previous work of single-axis (Carr-Purcell-Meiboom-Gill) DD towards the preservation of arbitrary spin states. After performing a detailed analysis of pulse and detuning errors, we compare the performance of various DD protocols. We identify that the concatenated XY8 pulse sequences serves as the optimal control scheme for preserving an arbitrary spin state. Finally, we use the concatenated sequences to demonstrate an immediate improvement of the AC magnetic sensitivity up to a factor of two at 250 kHz. For future work, similar protocols may be used to increase coherence times up to NV-NV interaction time scales, a major step toward the creation of quantum collective NV spin states.}, booktitle={SPIE Proceedings}, publisher={SPIE}, author={Farfurnik, D. and Jarmola, A. and Pham, L. M. and Wang, Z. H. and Dobrovitski, V. V. and Walsworth, R. L. and Budker, D. and Bar-Gill, N.}, editor={Stuhler, Jürgen and Shields, Andrew J.Editors}, year={2016}, month={Apr} }
 @inproceedings{farfurnik_2015, title={Enhanced coherence properties and solid-state spin ensemble magnetometry using optimized dynamical decoupling}, booktitle={The Israel Physical Society Annual Meeting}, author={Farfurnik, D.}, year={2015}, month={Dec} }
 @article{farfurnik_jarmola_pham_wang_dobrovitski_walsworth_budker_bar-gill_2015, title={Optimizing a dynamical decoupling protocol for solid-state electronic spin ensembles in diamond}, volume={92}, DOI={10.1103/physrevb.92.060301}, abstractNote={In this study, we demonstrate significant improvements of the spin coherence time of a dense ensemble of nitrogen-vacancy (NV) centers in diamond through optimized dynamical decoupling (DD). Cooling the sample down to 77 K suppresses longitudinal spin relaxation T1 effects and DD microwave pulses are used to increase the transverse coherence time T2 from ~0.7ms up to ~30ms. Furthermore, we extend previous work of single-axis (Carr-Purcell-Meiboom-Gill) DD towards the preservation of arbitrary spin states. Following a theoretical and experimental characterization of pulse and detuning errors, we compare the performance of various DD protocols. We also identify that the optimal control scheme for preserving an arbitrary spin state is a recursive protocol, the concatenated version of the XY8 pulse sequence. The improved spin coherence might have an immediate impact on improvements of the sensitivities of ac magnetometry. Moreover, the protocol can be used on denser diamond samples to increase coherence times up to NV-NV interaction time scales, a major step towards the creation of quantum collective NV spin states.}, number={6}, journal={Physical Review B}, publisher={American Physical Society (APS)}, author={Farfurnik, D. and Jarmola, A. and Pham, L. M. and Wang, Z. H. and Dobrovitski, V. V. and Walsworth, R. L. and Budker, D. and Bar-Gill, N.}, year={2015}, month={Aug} }
 @article{danan_farfurnik_bar-ad_vaidman_2015, title={Response: Commentary: “Asking photons where they have been” - without telling them what to say}, volume={3}, DOI={10.3389/fphy.2015.00048}, abstractNote={Citation: Danan A, Farfurnik D, Bar-Ad S and Vaidman L (2015) Response: Commentary: " Asking photons where they have been "-without telling them what to say. A commentary on Commentary: " Asking photons where they have been "-without telling them what to say In a recent Commentary, Salih [1] claims that we " devised an elegant experiment investigating the past of photons inside two Mach-Zehnder interferometers, one inside the other-yet drew the wrong conclusions [2]. " He also argues that the story told by the two-state vector formalism (TSVF) that we advocate, is contradictory. Here we answer Salih's criticism. Salih considers three possible options for the past of photons in our experiment and argues that option (1) according to which the photons are present in paths A and B simultaneously, is ruled out. To support his claim he notices that the product of projections on A and on B vanishes. However, for pre-and post-selected systems, as the photons in our experiment, the product rule does not hold [3], and therefore, his argument fails. The photon was in A and in B because it left traces in both places and this is the criterion of the past of the particle we rely on Vaidman [4]. An unavoidable non-vanishing interaction with the environment leads to a " weak measurement " of the presence of the photon in various places inside the interferometer exhibiting " weak-measurement elements of reality " [5]. Our claim, indeed, looks paradoxical. Even if the photon left very small traces in both places, there is a nonvanishing probability that the traces will be identified with certainty. In this case a single photon will be found in two places simultaneously. This is a contradiction: a single photon cannot be detected simultaneously in two places even in a non-demolition measurement. The resolution of the paradox is that the traces in A and in B are entangled and simultaneous detection of the photon in two places cannot happen. The photon changes the reduced density matrix in A and, also, the reduced density matrix in B, but, if this change is detected in A, then the reduced density matrix in B becomes identical to the undisturbed density matrix there, and vice versa. Salih considers a modification of our experiment in which, as he correctly states, we will not observe the presence of the photons in A and in B. However, it is not …}, journal={Frontiers in Physics}, publisher={Frontiers Media SA}, author={Danan, Ariel and Farfurnik, Demitry and Bar-Ad, Shimshon and Vaidman, Lev}, year={2015}, month={Jun} }
 @article{danan_farfurnik_bar-ad_vaidman_2013, title={Asking Photons Where They Have Been}, volume={111}, DOI={10.1103/physrevlett.111.240402}, abstractNote={We present surprising experimental evidence regarding the past of photons passing through an interferometer. The information about the positions through which the photons pass in the interferometer is retrieved from modulations of the detected signal at the vibration frequencies of mirrors the photons bounce off. From the analysis we conclude that the past of the photons is not represented by continuous trajectories, although a "common sense" analysis adopted in various welcher weg measurements, delayed-choice which-path experiments, and counterfactual communication demonstrations yields a single trajectory. The experimental results have a simple explanation in the framework of the two-state vector formalism of quantum theory.}, number={24}, journal={Physical Review Letters}, publisher={American Physical Society (APS)}, author={Danan, A. and Farfurnik, D. and Bar-Ad, S. and Vaidman, L.}, year={2013} }