The data is organized in folders as follows:

figures/
| - 1/
|   | - 1b/
|   | - 1c/
|   | - 1d/
| - 2/
| - 3/
| - 4/
|   | - 4a/
|   | - 4b/
| - 5/
|   | - 5a/
|   | - 5b/
| - s4/
| - s6/
| - s8/
| - s10/
| - s13/
| - s14/
| - s15/
| - s16/
| - s17/
| - s18/
misc/
| - ellipsometer/

Notes

Please refer to the main manuscript and supplementary text for additional details regarding the data files, e.g., the measurement and analysis protocols utilized.

Most of the data files may be readily loaded into a Python analysis script as pandas DataFrames. Please refer to pandas documentation for details.

Detector naming note: The 1550a, 1550b, 810a, and 810b labels in data files that contain them refer to the four detectors used in the experiment. "1550a_810a" therefore refers to coincidences between the 1550a and 810a detectors.

Three common types of "counts" appear in the data:

1. Single counts: Detection events on individual detectors.
2. Coincidence counts: Both types of coincident detection counts (coincidences and anti-coincidences). The individual coincidence channels are labeled such that coincidences and anti-coincidences may be clearly identified.
3. Accidental counts: Coincident detection counts resulting from uncorrelated photon pairs.

File descriptions and uses are given below.

Figures

1b

Contents

accidentals\raw_acc_X.json
coincidences\raw_coin_X.json

Description

These JSON files contain the coincidence and accidental counts for each of the 36 projective measurements for a quantum state tomography. The file names are numbered from 0 through 9 (ten trials).

Uses

1. Figs. 1B and S5 (density matrices)
2. Entanglement source purity, concurrence, and entangled singlet fraction

1c

Contents

1c.csv

Description

This file contains single, coincidence, and accidental counts for each trombone stage position from a fringe scan. There are 13 columns:

1. trombone_pos: Trombone stage position (μm)
2. sing_1550a: Single counts
3. sing_1550b: Single counts
4. sing_810a: Single counts
5. sing_810b: Single counts
6. coin_1550a_810a: Coincidence counts
7. coin_1550a_810b: Coincidence counts
8. coin_1550b_810a: Coincidence counts
9. coin_1550b_810b: Coincidence counts
10. acc_1550a_810a: Accidental counts
11. acc_1550a_810b: Accidental counts
12. acc_1550b_810a: Accidental counts
13. acc_1550b_810b: Accidental counts

Uses

1. Fig. 1C
2. Fringe fitting (period and visibility)
3. Mean total coincident detections per measurement
4. Mean coincidence to accidentals ratio per measurement
5. Classical Fisher information (estimated resolution and saturation of the Cramér–Rao bound)

1d

Contents

1d.csv

Description

This file contains fringe scan data for 41 coarse trombone positions. There are 83 columns:

1. trombone_pos: List of coarse trombone positions where fringe scans were performed (mm)
2. 12.647_xs: Fringe scan at position 12.647 mm, x values (fine trombone position, μm)
3. 12.647_ys: Fringe scan at position 12.647 mm, y values (coincidence probability)
4. 40 more sets of columns 2-3 for 40 additional coarse trombone positions

Uses

1. Fig. 1D
2. Full width at half maximum of the envelope of the modulated interference dip
3. Maximum fringe visibility expected from envelope fit
4. Fig. S9

2

Contents

displacements.csv
reference_fringe.csv

Description

displacements.csv: This file contains data for 100 trials of the measurement shown in Fig. 2. Each row gives the coincidence counts for a set displacement. There are 401 columns:

1. set_displacements: The set displacements introduced by the trombone stage (nm)
2. trial_0_1550a_810a: Coincidence counts
3. trial_0_1550a_810b: Coincidence counts
4. trial_0_1550b_810a: Coincidence counts
5. trial_0_1550b_810b: Coincidence counts
6. 99 more sets of columns 2-5 for Trials 1 through 99

reference_fringe.csv: The reference interference fringes used to extract displacement values from the coincidence counts in displacements.csv. This file contains coincidence counts for each trombone stage position from a fringe scan. There are 5 columns:

1. trombone_pos: Trombone stage position (μm)
2. coin_1550a_810a: Coincidence counts
3. coin_1550a_810b: Coincidence counts
4. coin_1550b_810a: Coincidence counts
5. coin_1550b_810b: Coincidence counts

Uses

1. Fig. 2

3

Contents

3a_repeated_measurements/repeated_measurement_count_time_X.csv (10 files)
3a_reference_fringe.csv

Description

repeated_measurement_count_time_X.csv: This file contains data for 100 trials for the data point shown in Fig. 3A corresponding to an integration time of X seconds. For filenames where X contains a "p" character, e.g., 0p1, the integration time X should be interpreted as containing a decimal point, e.g., 0.1 seconds. Positions x0 and x1 refer to the two positions on the sample being measured. Each file has 10 columns:

1. sample_x0_pos: Sample x0 positions (mm)
2. coin_1550a_810a_x0: Coincidence counts
3. coin_1550a_810b_x0: Coincidence counts
4. coin_1550b_810a_x0: Coincidence counts
5. coin_1550b_810b_x0: Coincidence counts
6. sample_x1_pos: Sample x1 positions (mm)
7. coin_1550a_810a_x1: Coincidence counts
8. coin_1550a_810b_x1: Coincidence counts
9. coin_1550b_810a_x1: Coincidence counts
10. coin_1550b_810b_x1: Coincidence counts

Each column has 100 rows; each row represents one trial.

3a_reference_fringe.csv: The reference interference fringes used to extract displacement values from the coincidence counts in repeated_measurement_count_time_X.csv. This file contains coincidence counts for each trombone stage position from a fringe scan. There are 5 columns:

1. trombone_pos: Trombone stage position (μm)
2. coin_1550a_810a: Coincidence counts
3. coin_1550a_810b: Coincidence counts
4. coin_1550b_810a: Coincidence counts
5. coin_1550b_810b: Coincidence counts

Uses:

1. Fig. 3A
2. Baseline detection rate, uncoated and coated wafer regions (Fig. 3A)
3. Interferometer resolution as a function of measurement time

4a

Contents

4a_classical.csv
4a_leakage.csv
4a_quantum.csv

Description

4a_classical.csv: This file contains data for the classical interference visibility as a function of the loss half-wave plate (HWP) angle. There are 38 columns:

1. loss_hwp_angles: The angle of the loss HWP with respect to the angle of maximum transmission (degrees)
2. count_times: The count time per point for the fringe scan for the given loss HWP angle setting (s)
3. 0.0_trombone_pos: Trombone stage position data for the fringe scan (HWP angle 0.0 degrees) (μm)
4. 0.0_sing_1550a: Single counts (HWP angle 0.0 degrees)
5. 0.0_sing_1550b: Single counts (HWP angle 0.0 degrees)
6. 11 more sets of columns 3-5, for each loss HWP angle setting

4a_leakage.csv: This file contains total coincidence and accidental counts (sum of 1550A-810A, 1550A-810B, 1550B-810A, 1550B-810B) collected over 1000 seconds with the entanglement source pumped at the same power as the data given in 4a_quantum.csv (3 mW). The counts were collected with mode b of the interferometer blocked. Dividing the total counts by 1000 seconds yields the average per-second rate of both the 1550-nm and 810-nm photons leaking into the lossless port of the interferometer. There are two columns:

1. coin_leakage: Total coincidence counts
2. acc_leakage: Total accidental counts

4a_quantum.csv: This file contains data for the quantum interference visibility as a function of the loss half-wave plate (HWP) angle. There are 110 columns:

1. loss_hwp_angles: The angle of the loss HWP with respect to the angle of maximum transmission (degrees)
2. count_times: The count time per point for the fringe scan for the given loss HWP angle setting (s)
3. 0.0_trombone_pos: Trombone stage position data for the fringe scan (HWP angle 0.0 degrees) (μm)
4. 0.0_coin_1550a_810a: Coincidence counts
5. 0.0_coin_1550a_810b: Coincidence counts
6. 0.0_coin_1550b_810a: Coincidence counts
7. 0.0_coin_1550b_810b: Coincidence counts
8. 0.0_acc_1550a_810a: Accidental counts
9. 0.0_acc_1550a_810b: Accidental counts
10. 0.0_acc_1550b_810a: Accidental counts
11. 0.0_acc_1550b_810b: Accidental counts
12. 11 more sets of columns 3-11, for each loss HWP angle setting

Uses

1. Fig. 4A

4b

Contents

classical/fringe_scan_c_background_X.csv (14 files)
quantum/fringe_scan_q_background_0.csv (14 files)

Description

fringe_scan_c_background_X.csv: These files contain data for the classical interference visibility as a function of background. X indicates the trial number. X = 0 has no external background, X = 1-13 have various levels of external background. Each file contains data for a single fringe scan (stage position and singles counts). Each file has three columns:

1. trombone_pos: Trombone stage position (μm)
2. sing_1550a: Single counts
3. sing_1550b: Single counts

fringe_scan_q_background_X.csv: These files contain data for the quantum interference visibility as a function of background. X indicates the trial number. X = 0 has no external background, X = 1-13 have various levels of external background. Each file contains data for a single fringe scan (stage position, singles counts, and coincidence counts). Each file has nine columns:

1. trombone_pos: Trombone stage position (μm)
2. sing_1550a: Single counts
3. sing_1550b: Single counts
4. sing_810a: Single counts
5. sing_810b: Single counts
6. coin_1550a_810a: Coincidence counts
7. coin_1550a_810b: Coincidence counts
8. coin_1550b_810a: Coincidence counts
9. coin_1550b_810b: Coincidence counts

Uses

1. Fig. 4B

5a

Contents

test_sample_classical/test_sample_scan_c_X.csv (100 files)
test_sample_quantum/test_sample_scan_q_X.csv (100 files)
test_sample_vis_scan_c.csv
test_sample_vis_scan_q.csv

Description

These files contain measurement data for the test sample (5-nm thickness).

test_sample_classical/test_sample_scan_c_X.csv: Data for sample scan trial X (X goes from 0 through 99), using classical interference. Each file records single counts as a function of sample position. Each file has three columns:

1. sample_pos: Sample positions (mm)
2. sing_1550a: Single counts
3. sing_1550b: Single counts

test_sample_quantum/test_sample_scan_q_X.csv: Data for sample scan trial X (X goes from 0 through 99), using quantum interference. Each file records coincidence counts as a function of sample position. Each file has five columns:

1. sample_pos: Sample positions (mm)
2. coin_1550a_810a: Coincidence counts
3. coin_1550a_810b: Coincidence counts
4. coin_1550b_810a: Coincidence counts
5. coin_1550b_810b: Coincidence counts

test_sample_vis_scan_c.csv: Classical interference fringe scan data for sample positions 6.5 mm and 13.5 mm. There are 7 columns:

1. sample_pos: Sample positions (mm)
2. 6.5_trombone_pos: Trombone stage position data (μm) for the fringe scan at sample position 6.5 mm
3. 6.5_sing_1550a: Single counts data for the fringe scan at sample position 6.5 mm
4. 6.5_sing_1550b: Single counts data for the fringe scan at sample position 6.5 mm
5. 13.5_trombone_pos: Trombone stage position data (μm) for the fringe scan at sample position 13.5 mm
6. 13.5_sing_1550a: Single counts data for the fringe scan at sample position 13.5 mm
7. 13.5_sing_1550b: Single counts data for the fringe scan at sample position 13.5 mm

test_sample_vis_scan_q.csv: Quantum interference fringe scan data for multiple sample positions. There are 76 columns:

1. sample_pos: Sample positions (mm)
2. 6.5_trombone_pos: Trombone stage position data (μm) for the fringe scan at sample position 6.5 mm
3. 6.5_coin_1550a_810a: Coincidence counts data for the fringe scan at sample position 6.5 mm
4. 6.5_coin_1550a_810b: Coincidence counts data for the fringe scan at sample position 6.5 mm
5. 6.5_coin_1550b_810a: Coincidence counts data for the fringe scan at sample position 6.5 mm
6. 6.5_coin_1550b_810b: Coincidence counts data for the fringe scan at sample position 6.5 mm
7. 14 more sets of columns 2-6, for each sample position

Uses

1. Fig. 5A
2. Test sample thickness measurement, quantum
3. Test sample thickness measurement, classical
4. Change in interference visibility from uncoated to coated regions of test sample, quantum and classical
5. Quantum probe transmission through test sample (coated region)
6. Fitted beam 1/e^2 diameter

5b

Contents

afm_image.ibw
afm_profile.txt

Description

afm_image.ibw: Data file for the image shown in the top panel of Fig. 5B. Tilt correction applied. May be opened with Gwyddion (free and open-source software).

afm_profile.txt: x-y coordinates for the bottom panel plot. Obtained from afm_image.ibw

The images shown in Fig. 5B are flipped around the vertical axis for visual clarity purposes.

Uses

1. Fig. 5B
2. Test sample thickness measurement, atomic force microscope (AFM)

s4

Contents

532nm_spectrum.asc
810nm_spectrum.asc

Description

532nm_spectrum.asc: Spectrum for the 532-nm pump laser

810nm_spectrum.asc: Spectrum for the 810-nm photons

Both files have two columns:

1. [No Title]: Wavelength (nm)
2. [No Title]: Intensity (a.u.)

Uses

1. Fig. S4
2. Photon center wavelengths and bandwidths

s6

Contents

s6.csv

Description

Data file with coincidence counts as a function of time. There are five columns:

1. timestamp: In the format YYYY-MM-DD HH:MM:SS (24-hour clock)
2. coin_1550a_810a: Coincidence counts
3. coin_1550a_810b: Coincidence counts
4. coin_1550b_810a: Coincidence counts
5. coin_1550b_810b: Coincidence counts

Uses

1. Fig. S6

s8

Contents

s8.csv

Description

Knife-edge scan data. There are 12 columns:

1. z0_x_displacement
2. z0_x_scan_810
3. z0_x_scan_1550
4. z0_y_displacement
5. z0_y_scan_810
6. z0_y_scan_1550
7. z1_x_displacement
8. z1_x_scan_810
9. z1_x_scan_1550
10. z1_y_displacement
11. z1_y_scan_810
12. z1_y_scan_1550

The “displacement” columns indicate the knife-edge displacement (in mm). The “scan” columns give the corresponding normalized power for the indicated wavelength (810 nm or 1550 nm). X and Y indicate the scan direction (horizontal and vertical, respectively). z0 and z1 indicate the longitudinal positions (z0 = 0 mm, z1 = 45 mm).

Uses

1. Fig. S8
2. Mean 1/e^2 radii of the 1550-nm and 810-nm beams

s10

Contents

fringe_scan_1mW.csv
fringe_scan_2mW.csv
fringe_scan_3mW.csv
fringe_scan_4mW.csv

Description

Fringe scan data for pump powers of 1, 2, 3, and 4 mW. Each file contains single, coincidence, and accidental counts for each trombone stage position from a fringe scan. Each file has 13 columns:

1. trombone_pos: Trombone stage position (μm)
2. sing_1550a: Single counts
3. sing_1550b: Single counts
4. sing_810a: Single counts
5. sing_810b: Single counts
6. coin_1550a_810a: Coincidence counts
7. coin_1550a_810b: Coincidence counts
8. coin_1550b_810a: Coincidence counts
9. coin_1550b_810b: Coincidence counts
10. acc_1550a_810a: Accidental counts
11. acc_1550a_810b: Accidental counts
12. acc_1550b_810a: Accidental counts
13. acc_1550b_810b: Accidental counts

Uses

1. Figure S10
2. Detected pair rate of at least 150,000 per second (interferometer)
3. Coincidence to accidental ratio, 1 mW and 3 mW

s13

Contents

s13.csv

Description

Knife-edge scan data. There are 12 columns:

1. x_displacement: Knife-edge displacements, x-scan (mm)
2. x_sing_1550a: Single counts
3. x_sing_1550b: Single counts
4. x_sing_810a: Single counts
5. x_sing_810b: Single counts
6. y_displacement: Knife-edge displacements, y-scan (mm)
7. y_sing_1550a: Single counts
8. y_sing_1550b: Single counts
9. y_sing_810a: Single counts
10. y_sing_810b: Single counts

X and Y indicate the scan direction (horizontal and vertical, respectively).

Uses

1. Fig. S13
2. Mean effective probe beam 1/e^2 diameter

s14

Contents

calibration_sample_quantum/calibration_sample_scan_q_X.csv (100 files)
calibration_sample_vis_scan_c.csv
calibration_sample_vis_scan_q.csv

Description

These files contain measurement data for the calibration sample (50-nm thickness).

calibration_sample_quantum/calibration_sample_scan_q_X.csv: Data for sample scan trial X (X goes from 0 through 99), using quantum interference. Each file records coincidence counts as a function of sample position. Each file has five columns:

1. sample_pos: Sample positions (mm)
2. coin_1550a_810a: Coincidence counts
3. coin_1550a_810b: Coincidence counts
4. coin_1550b_810a: Coincidence counts
5. coin_1550b_810b: Coincidence counts

calibration_sample_vis_scan_c.csv: Classical interference fringe scan data for sample positions 6.5 mm and 13.5 mm. There are 7 columns:

1. sample_pos: Sample positions (mm)
2. 12.0_trombone_pos: Trombone stage position data (μm) for the fringe scan at sample position 12.0 mm
3. 12.0_sing_1550a: Single counts data for the fringe scan at sample position 12.0 mm
4. 12.0_sing_1550b: Single counts data for the fringe scan at sample position 12.0 mm
5. 5.5_trombone_pos: Trombone stage position data (μm) for the fringe scan at sample position 5.5 mm
6. 5.5_sing_1550a: Single counts data for the fringe scan at sample position 5.5 mm
7. 5.5_sing_1550b: Single counts data for the fringe scan at sample position 5.5 mm

calibration_sample_vis_scan_q.csv: Quantum interference fringe scan data for multiple sample positions. There are 71 columns:

1. sample_pos: Sample positions (mm)
2. 12.0_trombone_pos: Trombone stage position data (μm) for the fringe scan at sample position 12.0 mm
3. 12.0_coin_1550a_810a: Coincidence counts data for the fringe scan at sample position 12.0 mm
4. 12.0_coin_1550a_810b: Coincidence counts data for the fringe scan at sample position 12.0 mm
5. 12.0_coin_1550b_810a: Coincidence counts data for the fringe scan at sample position 12.0 mm
6. 12.0_coin_1550b_810b: Coincidence counts data for the fringe scan at sample position 12.0 mm
7. 13 more sets of columns 2-6, for each sample position

Uses

1. Fig. S14
2. Quantum probe transmission through calibration sample (coated region)
3. Change in interference visibility from uncoated to coated regions of calibration sample, quantum and classical
4. Effective film refractive index, quantum probe

s15

Contents

scanning_stylus_image.bcrf
scanning_stylus_profiles.txt

Description

scanning_stylus_image.bcrf: Data file used to generate the profiles in scanning_stylus_profiles.txt. Tilt correction not applied. Note that a portion of the image is empty (no data). May be opened with Gwyddion (free and open-source software).

scanning_stylus_profiles.txt: Data for individual profiles obtained from scanning_stylus_image.bcrf (after tilt correction). There are 10 columns:

1. [Header rows]: X coordinates for horizontal profile 1 (m)
2. [Header rows]: Y coordinates for horizontal profile 1 (m)
3. Four more sets of X-Y coordinates for horizontal profiles 2 through 5

Uses

1. Fig. S15

s16

Contents

profiles\profile_X.csv
3d_optical_profilometer_image_height.csv
3d_optical_profilometer_image.cag
3d_optical_profilometer_image.xlsx

Description

profile_X.csv: x and z coordinates (in μm) for horizontal profile X (for six profiles numbered 1 through 6). Obtained from 3d_optical_profilometer_image.cag.

3d_optical_profilometer_image_height.csv: Height data exported from 3d_optical_profilometer_image.cag.

3d_optical_profilometer_image.cag: Data file used to generate the profiles in the profiles folder. Requires MultiFileAnalyzer software (Keyence Corporation). Proprietary software.

3d_optical_profilometer_image.xlsx: Image files exported from 3d_optical_profilometer_image.cag.

Uses

1. Fig. S16

s17

Contents

s17.csv

Description

This file contains single and coincidence counts for each trombone stage position from a fringe scan. There are 9 columns:

1. trombone_pos: Trombone stage position (μm)
2. sing_1550a: Single counts
3. sing_1550b: Single counts
4. sing_810a: Single counts
5. sing_810b: Single counts
6. coin_1550a_810a: Coincidence counts
7. coin_1550a_810b: Coincidence counts
8. coin_1550b_810a: Coincidence counts
9. coin_1550b_810b: Coincidence counts

Uses

1. Fig. S17

s18

Contents

s18.csv

Description

This file contains single, coincidence, and accidental counts for each trombone stage position from a fringe scan. There are 13 columns:

1. trombone_pos: Trombone stage position (μm)
2. sing_1550a: Single counts
3. sing_1550b: Single counts
4. sing_810a: Single counts
5. sing_810b: Single counts
6. coin_1550a_810a: Coincidence counts
7. coin_1550a_810b: Coincidence counts
8. coin_1550b_810a: Coincidence counts
9. coin_1550b_810b: Coincidence counts
10. acc_1550a_810a: Accidental counts
11. acc_1550a_810b: Accidental counts
12. acc_1550b_810a: Accidental counts
13. acc_1550b_810b: Accidental counts

Uses

1. Fig. S18
2. Fringe fitting (period and visibility)
3. Mean total coincident detections per measurement
4. Classical Fisher information (estimated resolution and saturation of the Cramér–Rao bound)

Misc

ellipsometer

Contents

calibration_ellipsometer.dat

Description

This file contains ellipsometer measurement data for the calibration sample (50-nm thickness). The file was generated by WVASE software (J.A. Woollam Co., Inc.). In addition to the header rows with measurement details, there are 6 columns:

1. [No title]: Wavelength (nm)
2. [No title]: Angle of incidence (degrees)
3. [No title]: Psi (degrees)
4. [No title]: Delta (degrees)
5. [No title]: Standard deviation, Psi (degrees)
6. [No title]: Standard deviation, Delta (degrees)

Uses

1. Nickel film refractive index, 1550 nm