Stable Three-Axis Nuclear Spin Gyroscope in Diamond

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Figure 1  Conceptual design of the nNV gyro. A slab of diamond of dimensions (2.5×2.5)mm2×150μm is anchored to the device body. Radio-frequency (rf) coils and microwave (μw) co-planar waveguides are fabricated on the diamond for fast control. NV centers are polarized by a green laser (532 nm), and state-dependent fluorescence intensity (637 nm) is collected employing a side-collection technique [11]. A second set of rf coils rotate with respect to the diamond-chip frame, for example, by being attached to one or more rings in a mechanical gimbal gyroscope (not shown). The 14N nuclear spins are used as probes of the relative rotation between the diamond frame and the external rf-coil frame. See Fig. 5 for a possible actual implementation.Figure 2  nNV-gyro control sequence. rf pulses, resonant with the quadrupolar transition of the 14N nuclear spin, are applied in a frame rotating at a rate Ω with respect to the diamond, thus, inducing a phase Ωt. The nuclear spin is first initialized by polarization transfer from the NV-electronic spin. An echo pulse is applied in the diamond frame to refocus static frequency shifts. Finally, Ω is extracted by mapping the nuclear-spin phase shift onto a population difference of the electronic spin and measuring the corresponding fluorescence intensity.Figure 3  nNV-gyro sensitivity in (mdegs−1)/Hz‾‾‾√ as a function of density η(n)=etmap/T∗2,NVet/T2,nCnV/4√t+td√t. Here, the exponential factors take into account the sensitivity degradation due to spin decoherence [12] with decay constants that depend on density, T2,n,T∗2,NV∝1/n (Appendix B). We considered a diamond chip of dimensions V=(2.5×2.5)mm2×150μm and assumed that only 1/4 of the NV spins were along the desired direction. The interrogation times were t=1ms (solid lines) and t=0.1ms (dashed line). The sensitivity for a simple Ramsey scheme (black lines) is limited by the nuclear spin T2,n=T∗2. Using an echo scheme (red thick line) improves the sensitivity, which is now limited by the coherence time T∗2,NV of the NV-electronic spin Figure 4  Signal Sc from the four classes of NV centers for a rotation Ω along an axis with angles θ=π/6 and ϕ=2π/3 from the [111] direction (which coincides with the first class of NVs, dashed-dotted line).Figure 5  Conceptual design of an integrated nNV-MEMS gyroscope, comprising a bulk acoustic wave (BAW) single-axis MEMS gyroscope [2] in an ∼800−μm diamond disk implanted with NV centers, whose nuclear spins form a spin gyroscope. (a) Schematic of the nNV-gyro operation. The spins implanted in the disk are polarized by an on-chip green laser. The electrodes surrounding the disk are silvered to allow for total internal reflection, and fluorescence is side collected [11] by replacing one of them by an on-chip optical waveguide at 638 nm. Strip lines for rf or μw control are fabricated on the disk. (b) Operation of the BAW mechanical gyroscope. The BAW is electrostatically driven in the second elliptic mode by an ∼10−kHz sinusoidal signal from the drive (blue) electrodes. A rotation out of the plane causes a decrease in the gap near the sense (grey) electrodes, leading to a capacitive measurement of the rotation [2]. Combinatoric filtering with the nNV measurement leads to noise rejection and improved stability.Figure 6  Polarization of the 14N nuclear spin under longitudinal driving of the NV-electronic transitions with a Rabi frequency of ΩR=500MHz, hyperfine A≈2.2MHz, and a static magnetic field of 20 G. The simulation includes dephasing of the electronic spin modeled by an Ornstein-Uhlenbeck process, yielding a T∗2 time of about 200 ns. To achieve high polarization, the process is repeated twice by repolarizing the NV-electronic spin (dashed line) via optical illumination.
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Inventors
Professor Paola Cappellaro
Department of Nuclear Science and Engineering, MIT
External Link (web.mit.edu)
Ashok Ajoy
Research Laboratory of Electronics, MIT
Managed By
Jim Freedman
MIT Technology Licensing Officer - Chemicals, Instruments, Consumer Products
Patent Protection

Stable three-axis nuclear spin gyroscope

US Patent Pending

Stable three-axis nuclear spin gyroscope

US Patent 9,417,068
Publications
Stable Three-Axis Nuclear Spin Gyroscope in Diamond
Physical Review A, 11 December 2012, Vol. 86, Iss. 6

Applications

This invention is used in navigation, inertial sensing, rotation sensors, mobile and geodetic applications.

Problem Addressed

The most widely used commercial gyroscopes are built using micro-electromechanical systems (MEMS) technology. Despite its several advantages over other systems, they suffer sensitivity drifts after a few minutes of operation. Therefore, there is a need for a commercial gyroscope that offers the advantages of MEMS-based systems with little or no sensitivity drift.

Technology

The invention overcomes the drawbacks of current gyroscopes by introducing a quantum sensor that provides a sensitive and stable three-axis gyroscope in the solid state. The Nitrogen-Vacancy (NV) based gyroscope includes a diamond structure implanted with multiple NV centers, whose nuclear spins form a spin gyroscope. A number of radio-frequency coils and microwave coplanar waveguides are fabricated on the diamond structure to provide a sensitive and stable three-axis gyroscope in the solid state.

Advantages

  • Better stability and higher sensitivity than conventional MEMS-based gyroscopes