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On-Chip Magnetic-Levitation Architecture

Updated 3 December 2025
  • On-chip magnetic-levitation architectures are microfabricated platforms that generate tailored 3D magnetic field gradients to stably levitate microscopic particles for quantum control and precision sensing.
  • These systems employ superconducting quadrupole traps, double-loop traps, and AC magnetic Paul traps, with tunable mode frequencies from tens of hertz to tens of kilohertz and varied operating temperatures.
  • Finite-element modeling confirms excellent agreement with experimental data on trap frequencies, quality factors, and dissipation mitigation, ensuring reliable integration with chip-based readout electronics.

On-chip magnetic-levitation architectures use lithographically patterned microfabricated coils or electrodes to produce field landscapes capable of stably levitating single microscopic particles above solid substrates. These platforms provide three-dimensional field gradients—magnetostatic or time-dependent—tailored for ultra-high mechanical quality factors, motional ground-state cooling, and integration with chip-based readout and feedback electronics. The architectures discussed here include superconducting quadrupole traps for Meissner-state diamagnetic spheres, double-loop planar coil traps, and AC magnetic Paul traps for ferromagnetic particles. Designs accommodate picogram to microgram masses and operate at cryogenic to room temperatures, with mode frequencies spanning tens of hertz up to tens of kilohertz, supporting quantum control and precision inertial sensing (Latorre et al., 2021, Latorre et al., 2022, 2002.03868, Janse et al., 13 Aug 2024).

1. Geometric Configurations and Fabrication

Architectures are categorized into three principal geometries: anti-Helmholtz-coil (AHC) quadrupole traps, planar double-loop (DL) traps, and planar AC magnetic Paul traps (MPT).

  • AHC Quadrupole Trap:
    • Implements two vertically displaced planar superconducting coils (typically Nb, thicknesses \sim300–1000 nm), patterned on double-side-polished Si chips, separated by 280 µm (Latorre et al., 2021, Latorre et al., 2022). Each coil features 10–20 windings of 30 µm ×\times 1 µm cross-section, width 2 µm, radial footprint \sim0.4 mm with a 200–300 µm central loading aperture. Fabrication uses DC magnetron sputtering, lithography, reactive-ion etch, deep Si etch (Bosch ICP), manual flip-chip stacking, Nb wire-bonding, and precision micro-manipulation for particle loading.
  • Double-Loop (DL) Trap:
    • Co-planar concentric Nb loops with opposing currents, diameters 12–18 µm, wire widths \sim1 µm, single-layer Nb (300 nm) on Si, electron-beam lithography plus ICP-RIE. A DL trap is fabrication-simplified, active for larger particles (\sim10 µm diameter) (2002.03868).
  • Planar AC Magnetic Paul Trap (MPT):
    • Two planar loops on PCB or silicon, inner radius R1=0.7R_1=0.7 mm, outer radius R2=1.4R_2=1.4 mm, track width 0.3 mm, thickness 35 µm (PCB) or 1–5 µm (on-chip Cu/Au). Concentric AC currents (+Itrap,ξItrap,ξ=2.22.4)(+I_\text{trap}, -\xi I_\text{trap}, \xi=2.2-2.4) null homogeneous AC field components, a central aperture \sim1 mm for particle injection. Potential on-chip implementation uses lift-off, damascene, DRIE, and anodic bonding (Janse et al., 13 Aug 2024).

Materials are selected for high jcj_c (Nb \sim3–5×1010\times10^{10}101110^{11} A/m2^2), with trap geometry, current capacity, and local surface field bounded by Meissner-state limitations (Bc1B_{c1}, λL\lambda_L).

2. Physical Principles and Trap Modeling

Levitation exploits strong field gradients for diamagnetic or paramagnetic force transduction. Quadrupole field patterns—static or oscillatory—produce spatial minima trapping particles in 3D.

  • Meissner-State Diamagnetism (Superconducting Sphere):
    • The potential U(r)=χVB(r)2/(2μ0)U(r)=-\chi V|B(r)|^2/(2\mu_0) (χ1\chi\approx-1 for ideal Meissner state) yields a restoring force F=UF=-\nabla U, with small oscillations governed by ωi2=(1/m)2U/xi2r0\omega_i^2 = (1/m)\partial^2U/\partial x_i^2|_{r_0} (Latorre et al., 2021, 2002.03868).
  • AC Magnetic Paul Trap (Ferromagnetic Cube):
    • An oscillating quadrupole field B1(r,t)=B1(xx^+yy^2zz^)cos(Ωt)\mathbf{B}_1(\mathbf r,t)=B_1''(x\hat{x}+y\hat{y}-2z\hat{z})\cos(\Omega t) produces a time-averaged ponderomotive potential, reducing to Mathieu equations for secular and micromotion dynamics, with parameters qz=2μB1/(mΩ2)q_z = 2\mu B_1''/(m\Omega^2), eigenfrequencies ωz=2ωx,y=B1Bsat/(μ0ρmΩ2)\omega_z = 2\omega_{x,y} = |B_1''|B_\text{sat}/(\mu_0\rho_m \Omega \sqrt{2}) (Janse et al., 13 Aug 2024).

Finite-element modeling (FEM, COMSOL Multiphysics) solves the Maxwell–London equations, incorporates finite λL\lambda_L, demagnetization, and flux quantization. For AHC and DL traps, FEM accounts for all coil, aperture, and particle effects, delivering quantitative predictions of B(x,y,z)B(x,y,z), levitation force, and stiffness. Meshing and convergence studies yield sub-1% agreement in trap frequencies, with mesh sizes 105\sim10^510610^6 DOF for 3D (2002.03868).

3. Experimental Parameters and Mode Characterization

  • Static Quadrupole Superconducting Trap:
    • Typical coil currents I=0.1I=0.1–$0.9$ A, stably levitating spheres in the $0.5$–$200$ µm range. Trap gradients G104G\sim10^4 T/m, trap depths U01017U_0\sim10^{-17} J (kB\gg k_B\times4K).Measuredtrapfrequenciesfor4850 µmPb/SnPbspheresat K). Measured trap frequencies for 48–50 µm Pb/SnPb spheres at I=0.5A: A: \omega_x/2\pi=3240Hz, Hz, \omega_y/2\pi=60Hz, Hz, \omega_z/2\pi=125130Hz(<ahref="/papers/2210.13451"title=""rel="nofollow"dataturbo="false"class="assistantlink"xdataxtooltip.raw="">Latorreetal.,2022</a>,<ahref="/papers/2109.15071"title=""rel="nofollow"dataturbo="false"class="assistantlink"xdataxtooltip.raw="">Latorreetal.,2021</a>).</li><li>Motionalmodequalityfactors Hz (<a href="/papers/2210.13451" title="" rel="nofollow" data-turbo="false" class="assistant-link" x-data x-tooltip.raw="">Latorre et al., 2022</a>, <a href="/papers/2109.15071" title="" rel="nofollow" data-turbo="false" class="assistant-link" x-data x-tooltip.raw="">Latorre et al., 2021</a>).</li> <li>Motional mode quality factors Q=3.4\times10^39.3\times10^3limitedbyeddycurrentdamping.Trapfrequenciesaretunable limited by eddy current damping. Trap frequencies are tunable \omega_i\propto Iinthe30160Hzrange.DuffingnonlinearitiesandintermodecouplingarequantifiedusingFEM,withquarticcoefficients in the 30–160 Hz range. Duffing nonlinearities and inter-mode coupling are quantified using FEM, with quartic coefficients \gamma_{ii}\sim10^210^3m m^{-2}ss^{-2}(<ahref="/papers/2210.13451"title=""rel="nofollow"dataturbo="false"class="assistantlink"xdataxtooltip.raw="">Latorreetal.,2022</a>).</li></ul></li><li><strong>AHCandDLTraps(Microscale):</strong><ul><li>AHCtraps( (<a href="/papers/2210.13451" title="" rel="nofollow" data-turbo="false" class="assistant-link" x-data x-tooltip.raw="">Latorre et al., 2022</a>).</li> </ul></li> <li><strong>AHC and DL Traps (Microscale):</strong> <ul> <li>AHC traps (\sim1 µmspheres, µm spheres, j=10^{11}A/m A/m^2)produce) produce \omega_x/2\pi=15.8kHz, kHz, \omega_y/2\pi=19.9kHz, kHz, \omega_z/2\pi=23.8kHz.DLtraps(10 µmsphere)yield kHz. DL traps (10 µm sphere) yield \omega_x/2\pi\sim82Hz(<ahref="/papers/2002.03868"title=""rel="nofollow"dataturbo="false"class="assistantlink"xdataxtooltip.raw="">2002.03868</a>).</li><li>Trapfrequencyscalingiscapturedby Hz (<a href="/papers/2002.03868" title="" rel="nofollow" data-turbo="false" class="assistant-link" x-data x-tooltip.raw="">2002.03868</a>).</li> <li>Trap frequency scaling is captured by \omega\sim\mu_0I/(r_\text{coil}^2R^{3/2}).</li></ul></li><li><strong>ACMagneticPaulTrap(RoomTemperatureFerromagnet):</strong><ul><li>250 µmedgecube,.</li> </ul></li> <li><strong>AC Magnetic Paul Trap (Room-Temperature Ferromagnet):</strong> <ul> <li>250 µm-edge cube, I_\text{trap}\sim1A, A, \Omega/2\pi=120Hz,yields Hz, yields (\omega_x,\omega_y,\omega_z)=2\pi\cdot(5.48,\,10.9,\,29.6)Hz.Librationalmodes Hz. Librational modes 2\pi\cdot(1362,1372)Hz.Qfactorspeakat Hz. Q-factors peak at \sim2,500,dominatedbyeddycurrents;vibrational, dominated by eddy currents; vibrational Q\sim10200(<ahref="/papers/2408.06838"title=""rel="nofollow"dataturbo="false"class="assistantlink"xdataxtooltip.raw="">Janseetal.,13Aug2024</a>).</li></ul></li></ul><h2class=paperheadingid=integratedreadoutandcouplingtechniques>4.IntegratedReadoutandCouplingTechniques</h2><p>Chipbasedplatformssupportintegrationofsuperconductingandmagneticreadouts.</p><ul><li><strong>DCSQUIDMagnetometry:</strong><ul><li>Superconductingpickuploops(L (<a href="/papers/2408.06838" title="" rel="nofollow" data-turbo="false" class="assistant-link" x-data x-tooltip.raw="">Janse et al., 13 Aug 2024</a>).</li> </ul></li> </ul> <h2 class='paper-heading' id='integrated-readout-and-coupling-techniques'>4. Integrated Readout and Coupling Techniques</h2> <p>Chip-based platforms support integration of superconducting and magnetic readouts.</p> <ul> <li><strong>DC-SQUID Magnetometry:</strong> <ul> <li>Superconducting pickup loops (L_\text{pickup}\sim0.7nH),offsetby nH), offset by \sim50 µm,coupledtocommercialDCSQUIDs(input µm, coupled to commercial DC-SQUIDs (input L_\text{in}\sim24nH,mutual nH, mutual M_\text{in}\sim0.87nH).Fluxtransferefficiency nH). Flux transfer efficiency \eta_\text{flux}\sim0.03;noisefloor; noise floor \Phi_\text{noise}\sim0.32m m\Phi_0/Hz/Hz^{1/2},displacementsensitivity, displacement sensitivity 200nm/Hz nm/Hz^{1/2}(x), (x), 100nm/Hz nm/Hz^{1/2}(y), (y), 17nm/Hz nm/Hz^{1/2}(z).ImprovedmatchingandpersistentcurrenttrapswillapproachtheintrinsicSQUIDnoise (z). Improved matching and persistent-current traps will approach the intrinsic SQUID noise 1\mu\Phi_0/Hz/Hz^{1/2}(<ahref="/papers/2210.13451"title=""rel="nofollow"dataturbo="false"class="assistantlink"xdataxtooltip.raw="">Latorreetal.,2022</a>).</li></ul></li><li><strong>ProspectiveHybridReadouts:</strong><ul><li>Onchipsuperconductingmicrowavecavities(sidebandcooling,groundstatecooling (<a href="/papers/2210.13451" title="" rel="nofollow" data-turbo="false" class="assistant-link" x-data x-tooltip.raw="">Latorre et al., 2022</a>).</li> </ul></li> <li><strong>Prospective Hybrid Readouts:</strong> <ul> <li>On-chip superconducting microwave cavities (sideband cooling, ground-state cooling \langle n\rangle<1),vectorresolvedinertialsensingarrays,andcouplingtoNVcentersforspinmechanics(<ahref="/papers/2408.06838"title=""rel="nofollow"dataturbo="false"class="assistantlink"xdataxtooltip.raw="">Janseetal.,13Aug2024</a>).</li></ul></li></ul><h2class=paperheadingid=dissipationstabilityandnoisemitigation>5.Dissipation,Stability,andNoiseMitigation</h2><p>Superconductingtrapsatcryogenictemperature(), vector-resolved inertial sensing arrays, and coupling to NV centers for spin-mechanics (<a href="/papers/2408.06838" title="" rel="nofollow" data-turbo="false" class="assistant-link" x-data x-tooltip.raw="">Janse et al., 13 Aug 2024</a>).</li> </ul></li> </ul> <h2 class='paper-heading' id='dissipation-stability-and-noise-mitigation'>5. Dissipation, Stability, and Noise Mitigation</h2> <p>Superconducting traps at cryogenic temperature (T=40mK4K)exhibitminimalintrinsicdissipation.Lifetimesexceeddaysintheabsenceofillumination.</p><ul><li><strong>PrimaryDissipationChannels:</strong><ul><li>Eddycurrentsinnearbynormalmetals,resistiveheatingofcoiltracks,technicalheatingorfluxtrappingfromopticalillumination(trappedparticlesreleasedafter mK–4 K) exhibit minimal intrinsic dissipation. Lifetimes exceed days in the absence of illumination.</p> <ul> <li><strong>Primary Dissipation Channels:</strong> <ul> <li>Eddy currents in nearby normal metals, resistive heating of coil tracks, technical heating or flux trapping from optical illumination (trapped particles released after \sim10scontinuousexposure)(<ahref="/papers/2109.15071"title=""rel="nofollow"dataturbo="false"class="assistantlink"xdataxtooltip.raw="">Latorreetal.,2021</a>,<ahref="/papers/2408.06838"title=""rel="nofollow"dataturbo="false"class="assistantlink"xdataxtooltip.raw="">Janseetal.,13Aug2024</a>).</li><li>InACPaultraps,eddycurrentdampingdominatesover<ahref="https://www.emergentmind.com/topics/geneticalgorithmsgas"title=""rel="nofollow"dataturbo="false"class="assistantlink"xdataxtooltip.raw="">gas</a>damping.Pressuredependenceisweak( s continuous exposure) (<a href="/papers/2109.15071" title="" rel="nofollow" data-turbo="false" class="assistant-link" x-data x-tooltip.raw="">Latorre et al., 2021</a>, <a href="/papers/2408.06838" title="" rel="nofollow" data-turbo="false" class="assistant-link" x-data x-tooltip.raw="">Janse et al., 13 Aug 2024</a>).</li> <li>In AC Paul traps, eddy-current damping dominates over <a href="https://www.emergentmind.com/topics/genetic-algorithms-gas" title="" rel="nofollow" data-turbo="false" class="assistant-link" x-data x-tooltip.raw="">gas</a> damping. Pressure dependence is weak (Qbarelyincreasesfrom barely increases from 1barto bar to 10^{-5}mbar).</li></ul></li><li><strong>MitigationStrategies:</strong><ul><li>Useofsuperconductingmicrostrips,superconductingshielding(Nb/Cryoperm),mechanicalisolation,removalofconductivecoatingsonparticles,carefulmatchingofcoilaperturesandseparation,persistentcurrentoperationtosuppresscurrentnoiseinducedflicker(<ahref="/papers/2210.13451"title=""rel="nofollow"dataturbo="false"class="assistantlink"xdataxtooltip.raw="">Latorreetal.,2022</a>,<ahref="/papers/2408.06838"title=""rel="nofollow"dataturbo="false"class="assistantlink"xdataxtooltip.raw="">Janseetal.,13Aug2024</a>).</li></ul></li></ul><h2class=paperheadingid=functionalimplicationsandapplications>6.FunctionalImplicationsandApplications</h2><p>Chipbasedmagneticlevitationenablesquantumoptomechanics,inertialandforcesensing,andfundamentalmacroscalequantumtests.</p><ul><li><strong>QuantumGroundStateCoolingandControl:</strong><ul><li>FEMmodelspredictchipscaletrapswith mbar).</li> </ul></li> <li><strong>Mitigation Strategies:</strong> <ul> <li>Use of superconducting microstrips, superconducting shielding (Nb/Cryoperm), mechanical isolation, removal of conductive coatings on particles, careful matching of coil apertures and separation, persistent-current operation to suppress current-noise-induced flicker (<a href="/papers/2210.13451" title="" rel="nofollow" data-turbo="false" class="assistant-link" x-data x-tooltip.raw="">Latorre et al., 2022</a>, <a href="/papers/2408.06838" title="" rel="nofollow" data-turbo="false" class="assistant-link" x-data x-tooltip.raw="">Janse et al., 13 Aug 2024</a>).</li> </ul></li> </ul> <h2 class='paper-heading' id='functional-implications-and-applications'>6. Functional Implications and Applications</h2> <p>Chip-based magnetic-levitation enables quantum optomechanics, inertial and force sensing, and fundamental macroscale quantum tests.</p> <ul> <li><strong>Quantum Ground-State Cooling and Control:</strong> <ul> <li>FEM models predict chip-scale traps with \nabla BenablingMHzscalecavitycoupling;feedback/sidebandprotocolsexpectedtoreachmotionalgroundstatein enabling MHz-scale cavity coupling; feedback/sideband protocols expected to reach motional ground state in <1ms.Lownoiseandhigh ms. Low noise and high Qopenaccesstomacroscalequantumsuperpositionsandtestsofcollapsemodels,decoherence,andgravity(<ahref="/papers/2210.13451"title=""rel="nofollow"dataturbo="false"class="assistantlink"xdataxtooltip.raw="">Latorreetal.,2022</a>,<ahref="/papers/2002.03868"title=""rel="nofollow"dataturbo="false"class="assistantlink"xdataxtooltip.raw="">2002.03868</a>).</li></ul></li><li><strong>PrecisionSensing:</strong><ul><li>Sensitivity open access to macroscale quantum superpositions and tests of collapse models, decoherence, and gravity (<a href="/papers/2210.13451" title="" rel="nofollow" data-turbo="false" class="assistant-link" x-data x-tooltip.raw="">Latorre et al., 2022</a>, <a href="/papers/2002.03868" title="" rel="nofollow" data-turbo="false" class="assistant-link" x-data x-tooltip.raw="">2002.03868</a>).</li> </ul></li> <li><strong>Precision Sensing:</strong> <ul> <li>Sensitivity a_\text{min} \sim S_F/(m \omega^2)with with m=7\times10^{-10}kg, kg, \omega/2\pi=100Hz, Hz, S_F\sim10^{-18}N/Hz N/Hz^{1/2}gives gives a_\text{min}\sim10^{-11}g/Hz/Hz^{1/2}(<ahref="/papers/2210.13451"title=""rel="nofollow"dataturbo="false"class="assistantlink"xdataxtooltip.raw="">Latorreetal.,2022</a>).Chiparraysallowvectorresolvedinertial/gravitationalsensingandtestsofshortrangeforces.</li></ul></li><li><strong>QuantumMagneticCoupling:</strong><ul><li>OnchipACMPTsformicronscaleferromagneticgrainsofferMHzlibrationalfrequencies,directmagneticcouplingtospins(NVcenters),andhighphononiccouplingstrengths (<a href="/papers/2210.13451" title="" rel="nofollow" data-turbo="false" class="assistant-link" x-data x-tooltip.raw="">Latorre et al., 2022</a>). Chip arrays allow vector-resolved inertial/gravitational sensing and tests of short-range forces.</li> </ul></li> <li><strong>Quantum-Magnetic Coupling:</strong> <ul> <li>On-chip AC MPTs for micron-scale ferromagnetic grains offer MHz librational frequencies, direct magnetic coupling to spins (NV centers), and high phononic coupling strengths g/2\pi\sim10100kHz(<ahref="/papers/2408.06838"title=""rel="nofollow"dataturbo="false"class="assistantlink"xdataxtooltip.raw="">Janseetal.,13Aug2024</a>).</li></ul></li><li><strong>ScalabilityandIntegration:</strong><ul><li>Scalingtosubmicronparticlesrequiresincreasing kHz (<a href="/papers/2408.06838" title="" rel="nofollow" data-turbo="false" class="assistant-link" x-data x-tooltip.raw="">Janse et al., 13 Aug 2024</a>).</li> </ul></li> <li><strong>Scalability and Integration:</strong> <ul> <li>Scaling to sub-micron particles requires increasing B_1''to to 10^6T/m T/m^2superconductingtracksorpulsedoperationforcurrentdensity,cryogenicanchoring,andmicrofluidicordielectrophoreticonchiploadingarenecessary.</li></ul></li></ul><h2class=paperheadingid=tablekeyexperimentalfeaturesofrepresentativearchitectures>Table:KeyExperimentalFeaturesofRepresentativeArchitectures</h2><divclass=overflowxautomaxwfullmy4><tableclass=tablebordercollapsewfullstyle=tablelayout:fixed><thead><tr><th>Architecture</th><th>TypicalParticleSize</th><th>TrapFrequencies</th><th>QualityFactor</th></tr></thead><tbody><tr><td>AHCQuadrupoleTrap</td><td>—superconducting tracks or pulsed operation for current density, cryogenic anchoring, and microfluidic or dielectrophoretic on-chip loading are necessary.</li> </ul></li> </ul> <h2 class='paper-heading' id='table-key-experimental-features-of-representative-architectures'>Table: Key Experimental Features of Representative Architectures</h2><div class='overflow-x-auto max-w-full my-4'><table class='table border-collapse w-full' style='table-layout: fixed'><thead><tr> <th>Architecture</th> <th>Typical Particle Size</th> <th>Trap Frequencies</th> <th>Quality Factor</th> </tr> </thead><tbody><tr> <td>AHC Quadrupole Trap</td> <td>1200 µm(Pb/SnPbsphere)</td><td> µm (Pb/SnPb sphere)</td> <td>32130Hz(exp),upto Hz (exp), up to 24kHz(FEM)</td><td> kHz (FEM)</td> <td>3.4\times10^39.3\times10^3</td></tr><tr><td>DLTrap</td><td></td> </tr> <tr> <td>DL Trap</td> <td>10 µm(sphere)</td><td> µm (sphere)</td> <td>82355Hz(FEM)</td><td>SimilartoAHC</td></tr><tr><td>PlanarACMPT</td><td> Hz (FEM)</td> <td>Similar to AHC</td> </tr> <tr> <td>Planar AC MPT</td> <td>250 µmcube(NdFeB)</td><td> µm cube (NdFeB)</td> <td>530Hzvib., Hz vib., 1.4kHzlibr.</td><td>Upto kHz libr.</td> <td>Up to 2,500$

Frequencies, materials, and Q-factors as reported in (Latorre et al., 2021, Latorre et al., 2022, 2002.03868, Janse et al., 13 Aug 2024).


On-chip magnetic levitation platforms advance precision control of massive quantum objects, offer scalable integration with superconducting electronics, and support multi-dimensional sensing schemes. Their design relies on careful coil geometry, low-dissipation refrigeration, and detailed electromagnetic modeling; levitation regimes, frequency scaling, and noise performance are in quantitative agreement with analytic and finite-element models. Persistent-current operation, microwave-cavity coupling, and hybrid quantum-mechanical protocols are under development, solidifying this architecture's role in next-generation quantum technology and inertial measurement (Latorre et al., 2021, Latorre et al., 2022, 2002.03868, Janse et al., 13 Aug 2024).

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