Magnetic Resonance Force Microscopy Measurement of Entangled Spin States

We simulate magnetic resonance force microscopy measurements of an entangled spin state. One of the entangled spins drives the resonant cantilever vibrations, while the other remote spin does not interact directly with the quasiclassical cantilever. The Schr\"odinger cat state of the cantilever reveals two possible outcomes of the measurement for both entangled spins.Comment: 3 pages RevTe

Quantitative Determination of the Adiabatic Condition Using Force-Detected Nuclear Magnetic Resonance

The adiabatic condition governing cyclic adiabatic inversion of proton spins in a micron-sized ammonium chloride crystal was studied using room temperature nuclear magnetic resonance force microscopy. A systematic degradation of signal-to-noise was observed as the adiabatic condition became violated. A theory of adiabatic following applicable to cyclic adiabatic inversion is reviewed and implemented to quantitatively determine an adiabaticity threshold $(\gamma H_1)^2/(\omega_{osc}\Omega) = 6.0$ from our experimental results.Comment: 5 pages, 3 fig

A Modified Approach to Single-Spin Detection Using Magnetic Resonance Force Microscopy

The magnetic moment of a single spin interacting with a cantilever in magnetic resonance force microscopy (MRFM) experiences quantum jumps in orientation rather than smooth oscillations. These jumps cannot be detected by a conventional MRFM based on observation of driven resonant oscillations of a cantilever. In this paper, we propose a method which will allow detection of the magnetic signal from a single spin using a modification of a conventional MRFM. We estimate the opportunity to detect the magnetic signal from a single proton.Comment: 4 pages LaTex, 4 figures in GIF forma

Spin Relaxation Caused by Thermal Excitations of High Frequency Modes of Cantilever Vibrations

We consider the process of spin relaxation in the oscillating cantilever-driven adiabatic reversals technique in magnetic resonance force microscopy. We simulated the spin relaxation caused by thermal excitations of the high frequency cantilever modes in the region of the Rabi frequency of the spin sub-system. The minimum relaxation time obtained in our simulations is greater but of the same order of magnitude as one measured in recent experiments. We demonstrated that using a cantilever with nonuniform cross-sectional area may significantly increase spin relaxation time.Comment: 12 pages RevTe

Nuclear magnetic resonance force microscopy with a microwire rf source

We use a 1.0-um-wide patterned Cu wire with an integrated nanomagnetic tip to measure the statistical nuclear polarization of 19F in CaF2 by magnetic resonance force microscopy (MRFM). With less than 350 uW of dissipated power, we achieve rf magnetic fields over 4 mT at 115 MHz for a sample positioned within 100 nm of the "microwire" rf source. A 200-nm diameter FeCo tip integrated onto the wire produces field gradients greater than 10^5 T/m at the same position. The large rf fields from the broadband microwire enable long rotating-frame spin lifetimes of up to 15 s at 4 K.Comment: 4 pages, 4 figure

Proton magnetic resonance imaging with a nitrogen-vacancy spin sensor

Nuclear magnetic resonance (NMR) imaging with nanometer resolution requires new detection techniques with sensitivity well beyond the capability of conventional inductive detection. Here, we demonstrate two dimensional imaging of $^1$H NMR from an organic test sample using a single nitrogen-vacancy center in diamond as the sensor. The NV center detects the oscillating magnetic field from precessing protons in the sample as the sample is scanned past the NV center. A spatial resolution of 12 nm is shown, limited primarily by the scan accuracy. With further development, NV-detected magnetic resonance imaging could lead to a new tool for three-dimensional imaging of complex nanostructures, including biomolecules.Comment: Main text: 19 pages including 5 figures Supplementary Information: 9 pages including 3 figure

Spurious harmonic response of multipulse quantum sensing sequences

Multipulse sequences based on Carr-Purcell decoupling are frequently used for narrow-band signal detection in single spin magnetometry. We have analyzed the behavior of multipulse sensing sequences under real-world conditions, including finite pulse durations and the presence of detunings. We find that these non-idealities introduce harmonics to the filter function, allowing additional frequencies to pass the filter. In particular, we find that the XY family of sequences can generate signals at the 2fac, 4fac and 8fac harmonics and their odd subharmonics, where fac is the ac signal frequency. Consideration of the harmonic response is especially important for diamond-based nuclear spin sensing where the NMR frequency is used to identify the nuclear spin species, as it leads to ambiguities when several isotopes are present.Comment: 6 pages, 7 figure

Feedback cooling of a cantilever's fundamental mode below 5 mK

We cool the fundamental mechanical mode of an ultrasoft silicon cantilever from a base temperature of 2.2 K to 2.9 +/- 0.3 mK using active optomechanical feedback. The lowest observed mode temperature is consistent with limits determined by the properties of the cantilever and by the measurement noise. For high feedback gain, the driven cantilever motion is found to suppress or "squash" the optical interferometer intensity noise below the shot noise level.Comment: 4 pages, 6 figure