QRAM
A multi‑domain sensing cartridge: three ribbons (optic • piezo • semiconductor) sandwich two parabolic‑well membranes that house spin‑coupled quantum‑dot lattices on both faces. Optics are run detuned & low‑duty with a photonic kill‑switch; membranes remain isolation homes only.
45–70 ns
Effective coherence (RT, upkeep strong)
8–12×
Conditioned SNR vs CCS (RT)
0.5–5 µs
Coherence at cryo (with upkeep)
6.6×
Relative SNR vs CCS (FIG.4 · Ti)
Key benefits
- Non‑invasive readout — membranes are never probed; all sensing is dispersive via ribbons.
- Heralded upkeep — detuned probe packets + micro‑trims extend usable windows without collapse.
- Optical kill‑switch — tunable evanescent overlap (≈5% → <1%) preserves passive lifetime.
- Modular cartridges — serviceable ribbon heads; drop‑in upgrades for optics/piezo/semiconductor.
- Cross‑domain gain — cones + parabolic wells funnel photons and amplify mount‑level motion.
- Balanced stack (FIG.4 · Ti) — best overall SNR; vacuum‑clean and mechanically robust.
- Multiple SKUs — NiTi (fatigue‑proof), ITO/Graphene (optics‑heavy), Flex Cu/PI (routing‑easy).
- Dark‑mode bias — lattice spacing favors subradiant modes for longer passive coherence.
- Backaction‑evading mechanics — strain node at membranes with two‑tone piezo drive.
Core performance (acceptance targets)
| Metric | Target | Notes |
|---|---|---|
| Effective coherence (RT, upkeep strong) | 45–70 ns | Heralded upkeep; detuned optics; ΔT_mem < 20 mK |
| Effective coherence (RT, no upkeep) | 10–15 ns | Optics present, low‑duty idle |
| Effective coherence (cryo + upkeep) | 0.5–5 µs | Optional validation tier |
| Relative SNR vs CCS | ≥ 6.5× | FIG.4 · Ti build, balanced optical/mech/electrical gains |
| Detuned probe regime | |Δ| = 30–60 meV | Flip sign for dispersive control |
| Evanescent overlap at membranes | 1–2% (idle), up to 5% (brief upkeep) | Photonic kill‑switch engaged |
| Upkeep packet width / rate | 1–5 ns @ 10–50 kHz | Mean photons per packet \u0304n ≈ 0.1–0.5 |
| Trim limits per cycle | Stark ≤ 1 meV; strain ≤ 0.5 µε | Applied via ribbons/anchors only |
Architecture & materials
Stack (top → bottom)
- Optic ribbon (waveguide + cones) with adjustable overlap
- Membrane A — parabolic wells; dots on both faces (isolation home)
- Piezo ribbon — backaction‑evading two‑tone; strain node at membranes
- Membrane B — parabolic wells; dots on both faces (isolation home)
- Semiconductor ribbon — field‑effect phase proxy; guard rings; no DC into membranes
Membranes: SiN / h‑BN / SiC (50–200 nm). Dots: giant‑shell CdSe/CdS or InP/ZnSeS with ALD Al₂O₃ cap (2–5 nm).
Recommended ribbon build (FIG.4 · Ti)
- SiN cap (150 nm) with parabolic wells
- ALD Al₂O₃ spacer (20–30 nm) — anti‑quench & isolation
- Titanium backbone (≈10 µm) — flexible, vacuum‑clean, conductive
- Perimeter guard ring; trace keep‑out under well field
Alternatives: NiTi (superelastic), ITO/Graphene hybrid (optical throughput), Flex Cu/PI (routing‑heavy).
Configurations
- Groups per ribbon (G): 8 / 16 / 24 standard: G16
- Dots per quadrant (N): 2 or 4 standard: N2 (even only)
- Optics: PAC‑O cones + windows; µLED/PD timing ready
- Tuning bins: H0/H1 (cone height), W0/W1 (well depth)
I/O & control (Plug‑and‑Play Integration Profile)
Optical
- Grating or fiber I/O; heterodyne LO input
- Detuned probe packets (1–5 ns); herald tap (90/10) to SPAD/SNSPD
- Photonic kill‑switch to set overlap 5% → <1%
Mechanical
- Two‑tone BAE drive (mounts); interferometric quadrature readout
- Phononic bandgap clamps; strain node at membranes
Electrical
- Field‑effect phase channel on semiconductor ribbon; guard rings
- Stark trim DAC (AC‑coupled) — ≤ 1 meV per upkeep cycle
- Star‑ground away from dot well region; leakage < pA
Controller No customer software
- Sealed hardware loop (analog/FPGA state machine); TTL/analog I/O only
- Front‑panel toggles: Detune ±, Power ½, Scramble, Upkeep On/Off
- No drivers or PC app required; logging optional via scope/time‑tagger
Harness & Adapters (Universal Wiring)
Universal harness on the ASU with swappable adapter tails so labs can use BNC/SMA/SHV/banana without custom wiring. Shields follow a star‑ground; membranes remain isolated.
Main control connector — Micro‑D 25 (QNH‑25)
| Pin | Name | Type / Level | Notes |
|---|---|---|---|
| 1 | GND_DIG | 0 V | Digital return |
| 2 | +5V_AUX | +5 V, 0.5 A | Accessory power (fused) |
| 3 | +12V_AUX | +12 V, 0.5 A | Accessory power (fused) |
| 4 | TRIG_IN | TTL 3–5 V | External packet trigger |
| 5 | HERALD_TTL | TTL 3–5 V | From SPAD/APD discriminator |
| 6 | GATE_OUT | TTL 3–5 V | Opens 20–50 ns read/trim gate |
| 7 | DETUNE_SEL | TTL | Detuning sign flip (+/−Δ) |
| 8 | SCRAMBLE_EN | TTL | Fake‑herald control |
| 9 | UPKEEP_EN | TTL | Enable upkeep loop |
| 10 | KILL_EN | TTL | Photonic kill‑switch actuator |
| 11 | STARK_SET | 0–5 V | Stark trim setpoint (AC‑coupled) |
| 12 | STARK_SENSE | 0–5 V | Monitor |
| 13 | PIEZO_TRIM | 0–10 V | Mount micro‑strain bias |
| 14 | PIEZO_SENSE | 0–10 V | Monitor |
| 15 | REF_CLK_IN | 3.3 V CMOS | 10 MHz reference |
| 16 | REF_CLK_OUT | 3.3 V CMOS | 10 MHz out |
| 17 | SDA | Service | Factory‑only |
| 18 | SCL | Service | Factory‑only |
| 19 | GND_ANA | 0 V | Analog return |
| 20 | CHASSIS_GND | Chassis | Bond to shell at ASU only |
| 21 | ID0 | Strap | Adapter ID |
| 22 | ID1 | Strap | Adapter ID |
| 23 | RSV1 | — | Reserved |
| 24 | RSV2 | — | Reserved |
| 25 | SHIELD | — | Connector shell |
RF & HV breakouts
| Port | Connector | Spec | Purpose |
|---|---|---|---|
| LO_IN | SMA‑F | 50 Ω, 0 dBm | Heterodyne local oscillator |
| EOM_DRIVE | SMA‑F | 50 Ω, up to +20 dBm | Probe packet modulation |
| PD_PHASE | SMA‑F | 50 Ω | Balanced PD → mixer (phase) |
| DITHER_REF | SMA‑F | 50 Ω | Piezo dither reference |
| PIEZO_HV | SHV | ±200 V max | Mount actuator HV |
Power
- Mini‑XLR‑4 24 VDC input (≤ 90 W). Pin‑1 GND, Pin‑4 +24 V. Internal rails: ±12 V, +5 V.
- Reverse‑polarity & surge protection onboard.
Adapter kits (pigtails)
- QNH‑BNC‑6: QNH‑25 → 6× BNC male (TRIG, HERALD, GATE, DETUNE, STARK, PIEZO_TRIM).
- QNRF‑SMA‑4: 4× SMA patch leads (LO, EOM, PD_PHASE, DITHER).
- QNHV‑SHV‑2: SHV male ↔ male HV lead (2 m, 5 kV rating).
- QNPWR‑MXLR: 24 VDC supply → mini‑XLR‑4 cable.
- ID straps: jumpers set ID0/ID1 so the unit auto‑scales ranges.
Shielding: braided overall shield to CHASSIS_GND at ASU (star ground). Coax shields both ends. TVS on externals. Membrane region remains floating.