Bulletin of the American Physical Society
APS March Meeting 2020
Volume 65, Number 1
Monday–Friday, March 2–6, 2020; Denver, Colorado
Session S09: Quantum Measurement and Sensing III |
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Sponsoring Units: DQI Chair: Leigh Norris, Dartmouth Coll Room: 106 |
Thursday, March 5, 2020 11:15AM - 11:27AM |
S09.00001: Observing a Topological Transition in Weak-Measurement-Induced Geometric Phases Yunzhao Wang, Kyrylo Snizhko, Alessandro Romito, Yuval Gefen, Kater Murch Quantum measurements induce backaction on quantum states resulting in measurement induced dynamics. A sequence of weak measurements can consequently realize a cyclic motion for the qubit state in Hilbert space and thus induce a geometric phase. As the measurement strength is varied between weak and strong regimes, we expect a topological transition corresponding to a change in the Chern number of the surface tracked by the qubit’s cyclic motion. To experimentally measure this transition, we employ quantum non-demolition measurement of a superconducting transmon circuit in the strong dispersive regime. This transition is revealed as a quantized jump in the averaged geometric phase when tuning the strength for the measurement sequence, giving new insights into how weak measurements are a powerful tool for quantum control. |
Thursday, March 5, 2020 11:27AM - 11:39AM |
S09.00002: Microscopic magnetometry of neurons using a superconducting flux qubit Hiraku Toida, Koji Sakai, Imran Mahboob, Tetsuhiko F. Teshima, Kousuke Kakuyanagi, Shiro Saito We have developed a microscopic magnetometer based on a superconducting flux qubit [1]. Using it, we have successfully obtained a magnetization signal from neurons. The neurons were cultured on parylene-C film in iron-rich medium to increase the number of spins in the cell. The film also worked as an insulator between the neurons and the flux qubit. The magnetization signal increased as a function of the inverse temperature and the Zeeman magnetic field. Considering that the control experiment without neurons showed no significant magnetization signal, this result strongly suggests that the signal originates from the spins in neurons. In the case of spins in neurons, because the spins distribute inhomogeneously in the cell, the contribution to the magnetization signal from the spins distant from the chip surface plays an important role, unlike the case of solid state spins [1]. To improve sensitivity to such widely distributed organic spins, a capacitively shunted flux qubit with a large loop size is developed and its design parameters are discussed [2]. [1] H. Toida et. al., Commun. Phys. 2, 33 (2019). [2] D. Marcos et. al., Phys. Rev. Lett. 105, 210501 (2010). |
Thursday, March 5, 2020 11:39AM - 11:51AM |
S09.00003: High contrast dual-mode optical and hyperpolarized 13C magnetic resonance imaging in diamond particles Xudong Lv, Jeffrey H Walton, Emanuel Druga, Fei Wang, Alessandra Aguilar, Tommy McKnelly, Raffi Nazaryan, Lan Wu, Olga Shenderova, Daniel Vigneron, Carlos Meriles, Jeffrey A Reimer, Alexander Pines, Ashok Ajoy Multichannel imaging - the ability to acquire images of an object through more than one imaging mode simultaneously - has opened exciting new avenues in several areas from astronomy to biomedicine. Visible optics and magnetic resonance imaging (MRI) offer complementary advantages of resolution, speed and depth of penetration, and as such would be attractive in combination. In this work, we integrate optical and MR imaging in diamond particles endowed with a high density of quantum defects, Nitrogen Vacancy (NV) centers. Under optical excitation, NV centers fluoresce brightly in the visible, as well as electron spin polarize, allowing the hyperpolarization of lattice 13C nuclei. Leveraging the ability of optical and MR imaging to simultaneously probe Fourier-reciprocal domains (real and k-space), we elucidate a hybrid sub-sampling protocol in both conjugate spaces to vastly accelerate dual-image acquisition, while concurrently reducing the net optical power, by two orders of magnitude in sparse-imaging scenarios. In addition, we demonstrate background-free imaging in optical and MR domains respectively. This work portends new avenues for quantum-enhanced dual-mode imaging platforms and opens possibilities for new therapeutic avenues including in low-field MRI-guided endoscopy. |
Thursday, March 5, 2020 11:51AM - 12:03PM |
S09.00004: Expanding the possibility of quantum metrology with a mixture of superpositions of marcoscopically distinct states Mamiko Tatsuta, Yuichiro Matsuzaki, Akira Shimizu A quantum sensor can beat the best sensitivity of a classical sensor, which is called the standard quantum limit (SQL), by the factor which scales with the square root of the system size. Sensitivity with such an enhancement is called the Heisenberg scaling. Although some specific examples that achieve the scaling have been studied, there is no general criteria about what kind of quantum states have the potential to achieve it. Here we prove that every state identified as a generalized cat state (GCS), i.e., superposition of macroscopically distinct states characterized by quantum coherence, can achieve it if used as a field sensor [1]. Importantly, even a mixture of exponentially large number of states can be identified as a GCS. We also show that GCSs beat the SQL in scaling despite the presence of dephasing which degrades the sensitivity. As a concrete example, we propose a protocol to generate a mixed GCS at finite temperature with donor spins in silicon. Its sensitivity is about 20 times better than that of a separable state even though it has an exponentially low purity. |
Thursday, March 5, 2020 12:03PM - 12:15PM |
S09.00005: Weak Measurements of a Superconducting Qubit Reconcile Incompatible Observables Jonathan Monroe, Taeho Lee, Nicole Yunger Halpern, Kater Murch Traditional uncertainty relations dictate a minimal amount of noise in incompatible projective quantum measurements. The noise comes from the observables' not sharing an eigenbasis. However, not all measurements are projective. In particular, weak measurements are minimally invasive tools for obtaining partial state information without projection. Weak measurements obey an entropic uncertainty relation based on generalized measurement operators [Yunger Halpern et al. Commun. Phys. 2, 92 (2019)]. We experimentally test the entropic uncertainty relation with strong and weak measurements of a superconducting transmon qubit. We find that a weak measurement can reconcile the incompatibility of two strong measurements via the weak measurement's backaction. |
Thursday, March 5, 2020 12:15PM - 12:27PM |
S09.00006: Control-enhanced quantum parameter estimation through reinforcement learning Han Xu, Xin Wang Measurement and estimation of parameters are indispensable for science and engineering. One of the main goals in parameter estimation is to find systematic schemes achieving high precision. Schemes for quantum parameter estimation could focus on optimizing the probe, its interaction with the system and measurements. Recently, schemes that add controls during the evolution are realized for significantly improving the precision. However, the identification of the control-enhanced scheme is usually computationally demanding, because the controls depend on the parameter value and need to be re-optimized after each update of the estimation. Here we show an efficient way to identify the controls through reinforcement learning that can improve the precision for both single-parameter estimation and multi-parameter estimation. Reinforcement learning also shows great generalizability, namely the neural network trained under a particular value of the parameter can work for different values within a broad range. These results suggest that reinforcement learning can be an efficient alternative to conventional optimal quantum control methods. |
Thursday, March 5, 2020 12:27PM - 12:39PM |
S09.00007: Optimal protocols for simultaneous measurement of multiple analytic functions with quantum sensor networks Jacob Bringewatt, Pradeep Niroula, Przemyslaw Bienias, Alexey V Gorshkov We expand on previous work for measuring analytic functions of input parameters of quantum sensor networks with qubit sensors. We consider the optimal bound with respect to different figures of merit for simultaneous measurement of multiple such analytic functions and propose protocols to achieve these bounds and thus Heisenberg scaling in the mean square error. We discuss conditions on the analytic functions where the possible speed-up over classical or sequential protocols is greatest and consider potential applications. |
Thursday, March 5, 2020 12:39PM - 12:51PM |
S09.00008: Optimal control for quantum detectors Paraj Titum, Kevin Schultz, Gregory Quiroz, David Clader Quantum systems are promising candidates for sensing of weak signals as they can provide unrivaled performance when estimating parameters of external fields. However, when trying to detect weak signals that are hidden by background noise, the signal to noise ratio is a more relevant metric than raw sensitivity. We identify, under modest assumptions about the statistical properties of the signal and noise, the optimal control to detect an external signal in the presence of background noise using a quantum sensor. We show this by considering the time-dependent control using the filter function formalism, and we use this formalism to derive the optimal protocol that maximizes the signal-to-noise ratio for the quantum detector. Interestingly, this optimal solution is the simple and well-known spin-locking control scheme. We further show, using numerical techniques, that this result is robust even when lifting some of our assumptions. These results show how that an optimal detection scheme can be easily implemented in near-term quantum sensors without the need for complicated pulse shaping. |
Thursday, March 5, 2020 12:51PM - 1:03PM |
S09.00009: Optimal Control and Glassiness in Quantum Sensing Christopher Timms, Michael Kolodrubetz The extreme responsiveness of qubits to their external environment has proven to be very useful for the purpose of quantum sensing. While this is valuable for sensing small target fields, this also makes the qubits very susceptible to disruption by external noise. We simulate the use of quantum optimal control to control the qubits for sensing protocols. Our work extends the pioneering results of Poggiali et al [PRX 8, 021059 (2018)] by allowing the use of non-pi pulses. We show that this added complexity translates into both improved sensitivity and qualitative modifications of the control landscape. In particular, we explore the connection of the rough control landscape to that of a (classical) spin glass and comment on possible applications of this connection to improving quantum sensing more broadly. |
Thursday, March 5, 2020 1:03PM - 1:15PM |
S09.00010: Statistical Certification of Majorana fermions Abu Ashik Md. Irfan, Karl Mayer, Gerardo Ortiz, Emanuel H Knill Physicists conjectured the existence of Majorana zero-energy modes in various condensed matter setups. Several experimental groups have even reported evidence of their existence by means that do not reflect or exploit its non-Abelian braiding statistics, a prerequisite for topological computation. What constitutes conclusive evidence for Majorana fermion detection? We present a quantum self-testing protocol that uses minimal assumptions and establishes strong conditions for Majorana fermion detection. We propose a contextuality witness W which consists of putative Majorana fermion parity operators. The resulting Bell-like inequality <W> ≤ 3 can be violated only if the system exhibits quantum contextuality. We further show that observing the ideal measurement statistics, leading to <W>=5, implies anticommutativity of the implemented Majorana fermion parity operators, a necessary prerequisite for the non-Abelian braiding statistics of Majoranas. Our protocol is robust to experimental errors. We obtain lower bounds on the fidelities of the state and measurement operators using both analytical calculations and a Semi Definite Programming approach. We also propose a protocol that certifies the gates which are implemented by the braiding of Majorana modes. |
Thursday, March 5, 2020 1:15PM - 1:27PM |
S09.00011: Demonstration and Application of Long-lived state in a four-spin system hyperpolarized at room temperature Koichiro Miyanishi, Naoki Ichijo, Makoto Motoyama, Akinori Kagawa, Makoto Negoro, Masahiro Kitagawa A solution with hyperpolarized nuclear spins encoded into a long-lived state has been utilized for sensing chemical phenomena in vivo and in vitro. In a conventional way, nuclear spins are hyperpolarized at very low temperatures, and it needs a large-scale setup with a cryogenic instrument. In this work, we demonstrate the encoding of a four-nuclear-spin system hyperpolarized at room temperature into a long-lived state in a solution. Both room temperature hyperpolarization and quantum encoded sensor are a hot topic in quantum sensing. Experiments are performed for the aromatic protons in p-chlorobenzoic acid. The lifetime of spin polarization was increased 2.4 times by the quantum encoding. We apply the solution with the long-lived state as a sensor in ligand--receptor binding experiments. |
Thursday, March 5, 2020 1:27PM - 1:39PM |
S09.00012: Diamond quantum DC magnetometer with efficient digital signal processing Yuta Masuyama, Takayuki Iwasaki, Mutsuko Hatano, Takeshi Ohshima Nitrogen-vacancy (NV) centers in diamond are promising solid-state quantum sensors. The sensor can potentially monitor the real-time magnetic field at room-temperature toward the brain-machine interface. One of the biggest challenges is to implement a highly sensitive sensor in a compact system. The sensor based on a digital signal processing with the Fourier transform has an advantage of its simpler system than an analog type, but it is hard to monitor the real-time magnetic field because the method needs many computational resources. |
Thursday, March 5, 2020 1:39PM - 1:51PM |
S09.00013: Magnetic Measurement of SPIONs using NVs in Diamond Maziar Saleh Ziabari, Pauli Kehayias, Jacob D Henshaw, Tzu-Ming Lu, Charles Harris, Edward S Bielejec, Dale L Huber, Victor Acosta, Michael P Lilly, Andrew M Mounce Superparamagnetic iron oxide nanoparticles (SPIONs) have numerous biological, magnetic, and chemical applications. Their nontoxicity and functionalizability supports medical applications as temporally and spatially controlled nanovectors for drug delivery, markers for enhanced MRI sensitivity, and for externally controlled hyperthermia in tumors. While bulk magnetic properties of SPIONs have been the subject of numerous studies, the magnetic properties of single SPIONs aren't well understood. Nitrogen vacancy defects in diamond are particularly suitable for characterizing isolated nanoparticles due to their extreme sensitivity to local magnetic fields. We characterize the magnetic properties of SPIONs of varying size and density, deposited on the surface of NV implanted diamond. |
Thursday, March 5, 2020 1:51PM - 2:03PM |
S09.00014: Imaging nanoscale volumes of single spins with shallow nitrogen-vacancy quantum spin sensors in diamond Zhiran Zhang, Dolev Bluvstein, Nicolas Ryan Williams, Ania Jayich The single shallow nitrogen-vacancy (NV) center, as an atomic-sized quantum sensor, can be incorporated with scanning probe microscopy with the potential of imaging single molecule structure with atomic-scale resolution. Here we present NV-based imaging of electron spins patterned on the nanoscale structure, where we employ DNA origami, a powerful molecular self-assembly platform, to enable bottom-up patterning of single spin-containing molecules. Such molecular structures can serve as two-dimensional calibration ‘spin’ rulers for the development of NV nanometrology. Specifically, we demonstrate the synthesis of the Gd chelate labeled DNA origami structures and present images of these structures acquired with NV center T1 imaging. Lastly, we discuss the outlook for our imaging technique to image spin-labelled molecules at the single spin level. |
Thursday, March 5, 2020 2:03PM - 2:15PM |
S09.00015: Time-resolved diamond magnetic microscopy of superparamagnetic nanoparticles Nate Ristoff, Abdelghani Laraoui, Ilja Fescenko, Joshua Damron, Nazanin Mosavian, Janis Smits, Andrey Jarmola, Pauli Kehayias, Maziar Salehziabari, Andrew M Mounce, Dale L Huber, Victor Acosta Magnetic nanoparticles have many biomedical applications including hyperthermia for cancer therapy, magnetic resonance imaging, and magnetic relaxation imaging. These applications require that the magnetic nanoparticles have uniform magnetic properties, size and morphology. We report progress on a nitrogen vacancy (NV) center widefield magnetic microscope which measures the Neel relaxation and hysteresis curve of many single magnetic nanoparticles. In addition, we report on progress to correlate these relaxation measurements to particles size via scanning electron microscope (SEM). |
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