Induction-detection electron spin resonance with spin sensitivity of a few tens of spins

Artzi, Yaron; Twig, Ygal; Blank, Aharon

doi:10.1063/1.4913806

Cited by 42 publications

(34 citation statements)

References 23 publications

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“…To increase the sensitivity, micro-fabricated metallic planar resonators with smaller mode volumes have been used, resulting in larger spin-microwave coupling [12,13]. Combined with operation at T = 4 K and the use of low-noise cryogenic amplifiers and superconducting high-Q thin-film resonators, sensitivities up to N min ∼ 10 7 spins have been reported, which represents the current state-of-the-art [14][15][16].Further improvements in the sensitivity of ESR spectroscopy can be obtained by cooling the sample and resonator down to mK temperatures that satisfy T hω 0 /k B at X-band frequencies. As a result, both the spins and the microwave field reach their quantum ground state, which is the optimal situation for magnetic resonance since the spins are then fully polarized and thermal noise suppressed.…”

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confidence: 99%

Reaching the quantum limit of sensitivity in electron spin resonance

et al. 2015

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1 arXiv:1507.06831v1 [quant-ph] Jul 2015The detection and characterization of paramagnetic species by electron-spin resonance (ESR) spectroscopy is widely used throughout chemistry, biology, and materials science [1], from in-vivo imaging [2] to distance measurements in spinlabeled proteins [3]. ESR typically relies on the inductive detection of microwave signals emitted by the spins into a coupled microwave resonator during their Larmor precession -however, such signals can be very small, prohibiting the application of ESR at the nanoscale, for example, at the single-cell level or on individual nanoparticles. In this work, using a Josephson parametric microwave amplifier combined with high-quality factor superconducting micro-resonators cooled at millikelvin temperatures, we improve the state-of-the-art sensitivity of inductive ESR detection by nearly 4 orders of magnitude. We demonstrate the detection of 1700 bismuth donor spins in silicon within a single Hahn [4] echo with unit signal-to-noise (SNR) ratio, reduced to just 150 spins by averaging a single Carr-Purcell-Meiboom-Gill sequence [5]. This unprecedented sensitivity reaches the limit set by quantum fluctuations of the electromagnetic field instead of thermal or technical noise, which constitutes a novel regime for magnetic resonance. The detection volume of our resonator is ∼0.02 nl, and our approach can be readily scaled down further to improve sensitivity, providing a new and versatile toolbox for ESR at the nanoscale.A wide variety of techniques are being actively explore to push the limits of sensitivity of ESR to the nanoscale, including approaches based on optical [6,7] or electrical [8,9] detection, as well as scanning probe methods [10,11]. Our focus in this work is to maximise the sensitivity of inductively detected pulsed ESR, in order to maintain the broad applicability to different spin species as well as fast high-bandwidth detection. Pulsed ESR spectroscopy proceeds by probing a sample coupled to a microwave resonator of frequency ω 0 and quality factor Q with sequences of microwave pulses that perform successive spin rotations, triggering the emission of a microwave signal called a spin-echo whose amplitude and shape contain the desired information about the number and properties of paramagnetic species. The spectrometer sensitivity is conveniently quantified by the minimal number of spins N min that can be detected within a single echo [4]. Conventional ESR spectrometers use 3D resonators with moderate quality factors in which the spins are only weakly coupled to the microwave photons and thus obtain a sensitivity of N min ∼ 10 13 spins at T = 300 K and X-band fre-2 quencies (ω 0 /2π ∼ 9 − 10 GHz). To increase the sensitivity, micro-fabricated metallic planar resonators with smaller mode volumes have been used, resulting in larger spin-microwave coupling [12,13]. Combined with operation at T = 4 K and the use of low-noise cryogenic amplifiers and superconducting high-Q thin-film resonators, sensitivities up to N min ∼ 10 7 spins have ...

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confidence: 99%

Reaching the quantum limit of sensitivity in electron spin resonance

et al. 2015

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“…Compared to other ultra-high sensitivity ESR measurements 22,23 , the use of Josephson junctions can increase significantly the spatial resolution of the magnetic detection while allowing an on-chip implementation. For instance, the magnetic signal of one nanoparticle is detectable if placed on the junction of a micrometer sized superconducting quantum interference device (micro-SQUID) 24 .…”

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Sensitive spin detection using an on-chip SQUID-waveguide resonator

Yue

Chen

Barreda

et al. 2017

Applied Physics Letters

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Precise detection of spin resonance is of paramount importance to achieve coherent spin control in quantum computing. We present a novel setup for spin resonance measurements, which uses a dc-SQUID flux detector coupled to an antenna from a coplanar waveguide. The SQUID and the waveguide are fabricated from 20 nm Nb thin film, allowing high magnetic field operation with the field applied parallel to the chip. We observe a resonance signal between the first and third excited states of Gd spins S = 7/2 in a CaWO 4 crystal, relevant for state control in multi-level systems.Solid state spin-based qubits are studied for quantum computing due to their relatively long coherence time 1,2 . Typical implementations of these qubits are molecule-based magnets 3-6 , nitrogen-vacancy (NV) centers in diamond 7 and quantum spins in crystals 8-11 . These spin-based qubits are designed such that the spins are well separated in the crystal, leading to an increased decoherence time due to weak spin dipolar interactions.Among the rare-earth ions, S-state lanthanide ions doped in a crystal have a rich energy level structure due to their large spin. Multi-level systems are promising for implementing few-qubits algorithms 12 or as quantum memories [13][14][15][16] . For quantum technology applications, a higher sensitivity electron spin resonance (ESR) measurement is needed to be able to manipulate spins in mesoscopic crystals placed on superconducting chips [17][18][19][20][21] .Compared to other ultra-high sensitivity ESR measurements 22,23 , the use of Josephson junctions can increase significantly the spatial resolution of the magnetic detection while allowing an on-chip implementation. For instance, the magnetic signal of one nanoparticle is detectable if placed on the junction of a micrometer sized superconducting quantum interference device (micro-SQUID) 24 . We present a novel setup for ESR measurements, which combines the high spin sensitivity of an on-chip micro-SQUID and the flexibility of a coplanar waveguide for microwave excitation. Different dc-SQUID implementations were also used to detect molecular 25,26 and diluted 27 spins. In our case, the coupling of the two devices generates a cavity effect, which amplifies the microwave power seen by the spins. When using micro-SQUIDs, the samples are positioned close to their loop for increased sensitivity since the device a) Electronic mail: gy10c@my.fsu.edu b) Electronic mail: ic@magnet.fsu. edu FIG. 1. (color online) Scanning electron micrograph of the device and of the micro-SQUID (inset). The darker (blue) area is the coplanar waveguide with the two Ω-loop shortcircuits between the central line and the lateral ground planes. The microwave excitation is depicted by the curvy arrow and an in-plane field B0 is generated by an external coil. The SQUIDs share a common ground (sketched as a white rectangle). Each SQUID has one I − V line shown in green for clarity in their narrowest region.can work under in-plane magnetic fields in the range of ∼Tesla [28][29][30] .Using this s...

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“…The magnitude of the echo signal acquired via this sequence is given by [39]: which we place miniature gradient coils that make it possible to produce powerful magnetic field gradients with a very short duration, as required by the PGSE sequence for electrons. Our latest achievements in this area allow us to obtain gradients of up to ~500 T/m with pulse duration of ~1μs [40]. Thus, even for a sample with ~10 14 P atoms in 1 cm 3 , it is possible, for example, to employ the sequence in Fig.…”

Section: Measurements Of Spin Diffusionmentioning

confidence: 99%

Direct Measurement of the Flip-Flop Rate of Electron Spins in the Solid State

et al. 2016

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Electron spins in solids have a central role in many current and future spinbased devices, ranging from sensitive sensors to quantum computers (QC). Many of these apparatuses rely on the formation of well-defined spin structures (e.g., a 2D array) with controlled and well-characterized spin-spin interactions. While being essential for device operation, these interactions can also result in undesirable effects, such as decoherence. Arguably, the most important pure quantum interaction that causes decoherence is known as the "flip-flop" process, where two interacting spins interchange their quantum state. Currently, for electron spins, the rate of this process can only be estimated theoretically, or measured indirectly, under limiting assumptions and approximations, via spin relaxation data. This work experimentally demonstrates for the first time how the flip-flop rate can be directly and accurately measured by examining spin diffusion processes in the solid state for physically fixed spins. Under such terms, diffusion can occur only through this flip-flop-mediated quantum state exchange and not via actual spatial motion. Our approach was implemented on two types of samples, phosphorus-doped 28 Si and nitrogen vacancies (NV) in diamond, both of which are significantly relevant to quantum sensors and information processing. However, while the results for the former sample are conclusive and reveal a flip-flop rate of ~12.3 Hz, for the latter sample only an upper limit of ~0.2 Hz for this rate could be estimated.

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Induction-detection electron spin resonance with spin sensitivity of a few tens of spins

Cited by 42 publications

References 23 publications

Reaching the quantum limit of sensitivity in electron spin resonance

Reaching the quantum limit of sensitivity in electron spin resonance

Sensitive spin detection using an on-chip SQUID-waveguide resonator

Direct Measurement of the Flip-Flop Rate of Electron Spins in the Solid State

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