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""" This module contains a dictionary of parameters (``params``) that is
used by ``qmix.exp.RawData`` and ``qmix.exp.RawData0`` to control
how experimental data is loaded and analyzed.
Note:
This dictionary just contains the default values. You can overwrite these
values by passing keyword arguments to ``RawData`` or ``RawData0``. For
example, the default value for voltage units is millivolts (``"mV"``).
You can change this parameter to be microvolts (``"uV"``) by passing
``v_fmt="uV"`` to ``RawData`` or ``RawData0``.
Also note that experimental data can be passed to ``RawData0`` and
``RawData`` either as CSV data files or as Numpy arrays. In both
cases, the data should have two columns: one for voltage and one
for current or IF power, depending on the file. See Example #3 on the
QMix website for more information.
All of the different parameters are described below along with their default
values.
**Parameters:**
- CSV files:
- **Note:** If you are using CSV files, these parameters control how
the data is loaded from the CSV files.
- ``delimiter = ","`` : The delimiter used by the CSV data files.
- ``usecols = (0,1)`` : Which columns to import from the CSV data
files.
- ``skip_header = 1`` : Number of rows to skip at the beginning CSV
data files. (Used to skip the header.)
- Units:
- ``v_fmt = "mV"`` : Units for imported voltage data. The options
are: ``"uV"``, ``"mV"`` and ``"V"``.
- ``i_fmt = "mA"`` : Units for imported current data. The options
are: ``"uA"``, ``"mA"`` and ``"A"``.
- Importing I-V data:
- ``vmax = 6e-3`` : Maximum voltage to import in units [V]. Used in
case the current is saturated beyond some bias voltage.
- ``npts = 6001`` : Number of points to use in the I-V data
interpolation.
- ``debug = False`` : If set to ``True``, this will plot each step of
the I-V data loading and analysis procedure. Note: This will
display 4 individual plots for each I-V curve that is loaded, so do
not use this if you are looping through multiple files.
- Correcting voltage/current offsets:
- **Note:** Sometimes there is an offset in the I-V data. The
parameters below can be used to correct this. If you know the
current and voltage offset, you can define ``ioffset`` and
``voffset``, respectively. Otherwise, ``RawData0`` will attempt to
find the offset on its own. This is done by taking the derivative
of the DC I-V curve, and then finding the maximum derivative value
between ``voffset_range[0]`` and ``voffset_range[1]``.
- ``ioffset = None`` : Offset of the DC tunneling current data in
units [A].
- ``voffset = None`` : Offset of the DC bias voltage data in units
[V].
- ``voffset_range = (-3e-4, 3e-4)`` : Voltage range over which to look
for the voltage offset in units [V]. The ``RawData0`` class will
look from ``voffset_range[0]`` to ``+voffset_range[1]`` for the
voltage offset.
- ``voffset_sigma = 1e-5`` : When looking for the voltage offset,
smooth the derivative of the DC I-V curve by convolving data with a
Gaussian distribution with this standard deviation.
- Correcting experimental I-V data:
- ``rseries = None`` : Correct for a series resistance in the DC
measurement system using this resistance in units [ohms]. Leave as
``None`` if there is no series resistance.
- ``i_multiplier = 1.`` : Multiply the imported I-V current by this
number. Used to correct for errors in the I-V readout.
- ``v_multiplier = 1.`` : Multiply the imported I-V voltage by this
number. Used to correct for errors in the I-V readout.
- Filtering I-V data:
- **Note:** When I-V data is loaded, it is normalized,
rotated 45 degrees, filtered using a Savitzky-Golay filter, and
then rotated back. (The rotation allows for good filtering
without smearing the transition.) The parameters below control this
process.
- ``filter_data = True`` : Filter the I-V data?
- ``filter_theta = 0.785`` : Angle by which to rotate the DC I-V curve
before filtering (in radians).
- ``filter_nwind = 21`` : Width of the Savitzky-Golay filter.
- ``filter_npoly = 3`` : Order of the Savitzky-Golay filter.
- Analyzing the DC I-V curve:
- ``vgap_threshold = 105e-6`` : Threshold current, in units [A], at
which to measure the gap voltage. (Note: the gap voltage is defined
here as the voltage at which the DC I-V curve crosses this current
value.)
- ``vrn = (3.5e-3, 4.5e-3)`` : Voltage range over which to calculate
the normal-state resistance, in units [V].
- ``vrsg = 2e-3`` : Voltage at which to measure the subgap resistance,
in units [V].
- ``vleak = 2e-3`` : Voltage at which to measure the leakage current,
in units [V].
- Analyzing pumped I-V data:
- ``analyze_iv = True`` : Analyze the pumped I-V data? This involves
a procedure to recover the embedding circuit.
- ``fit_range = (0.25, 0.8)`` : Fit interval for impedance recovery,
normalized to the width of the first photon step. For example, with
``(0.25, 0.8)``, the impedance recovery procedure will not
consider the first 25% of the first step or the last 20%. It will
only use the bias voltages between 25% and 80%. This is used to
select only the middle of the step.
- ``remb_range = (0, 1)`` : Range of embedding resistances to test,
normalized to the normal resistance.
- ``xemb_range = (-1, 1)`` : Range of embedding reactances to test,
normalized to the normal resistance.
- ``zemb = None`` : During impedance recovery, force the embedding
impedance to be this value (normalized).
- ``alpha_max = 1.5`` : Initial guess for the drive level (alpha)
during impedance recovery.
- ``num_b = 20`` : Maximum number of Bessel functions to include when
calculating the tunneling currents.
- Importing IF data:
- ``ifdata_npts = 3000`` : Number of points to use when interpolating
IF data.
- Filtering IF data:
- ``ifdata_sigma = 1e-5`` : Smooth the measured IF power data by
convolving it with a Gaussian distribution. This is the standard
deviation, in units [V].
- Analyzing the DC IF data:
- **Note:** DC IF data (IF power with no LO injection) is used to
measure the IF noise contribution and convert the power units into
units of temperature [K]. This is done by fitting a linear trend
to the shot noise present in the DC IF data.
- ``vshot = None`` : Voltage range over which to fit the shot noise
slope, in units [V]. Can be a list of lists to define multiple
ranges. For example, to fit the shot noise slope from 4-5 mV and
from 6-7 mV, you would pass ``vshot=((4e-3, 5e-3), (6e-3, 7e-3))``.
You can break it up this way in case there are Josephson effects
present in the IF power data.
- Analyzing pumped IF data (noise temperature analysis):
- ``analyze_if = True`` : Analyze the IF data? This involves
calculating the noise temperature and gain.
- ``t_cold = 78.`` : Temperature of the cold load (likely liquid
nitrogen), in units [K].
- ``t_hot = 293.`` : Temperature of the hot load (likely room
temperature), in units [K].
- ``vbest = None`` : Bias voltage at which to calculate the best noise
temperature value. If this value is set to ``None``, the ``RawData``
class will determine the best bias voltage automatically.
- ``best_pt = 'Max Gain'`` : Which bias voltage should we select as
the best bias? Where the gain is the highest (``'Max Gain'``)? Or
the lowest noise temperature (``'Min Tn'``)?
- IF response:
- ``ifresp_delimiter = '\\t'`` : Delimiter for IF spectrum files.
- ``ifresp_usecols = (0, 1, 2)`` : Columns to import from IF spectrum
files. The first column should be the frequency, the second should
be the IF power from the hot load, and the third should be the IF
power from the cold load.
- ``ifresp_skipheader = 1`` : Number of rows to skip at the beginning
of the IF spectrum file.
- ``ifresp_maxtn = 1e6`` : Maximum noise temperature. All values above
this value will be set to ``ifresp_maxtn``.
- Response function:
- **Note:** The ``RawData0`` class generates a response function
based on the imported DC I-V data (using ``qmix.respfn.RespFn``).
It also generates a second response function that is slightly
smeared. This smeared response function is useful for simulations
because it simulates a small amount of heating.
- ``v_smear = 0.020`` : Voltage smear of the "smeared" response
function.
- Plotting parameters:
- ``vmax_plot = 4.0`` : Maximum bias voltage for plots, in units [mV].
- Junction properties:
- ``area = 1.5`` : Area of the SIS junction in units [um^2].
- Local-oscillator (LO) signal:
- ``freq = None`` : Frequency of the local-oscillator signal in units
[GHz].
- Miscellaneous:
- ``comment = ""`` : Add a comment to describe this instance.
- ``verbose = True`` : Print information to the terminal.
"""
params = dict(
# CSV files
delimiter = ',',
usecols = (0, 1),
skip_header = 1,
# Units
v_fmt = 'mV',
i_fmt = 'mA',
# Importing I-V data
vmax = 6e-3,
npts = 6001,
debug = False,
# Correcting voltage/current offsets
ioffset = None,
voffset = None,
# Find voltage offset automatically
voffset_range = (-3e-4, 3e-4),
voffset_sigma = 1e-5,
# Correcting experimental I-V data
rseries = None,
i_multiplier = 1.,
v_multiplier = 1.,
# Importing IF data
ifdata_npts = 3000,
# Filtering I-V data
filter_data = True,
filter_theta = 0.785,
filter_nwind = 21,
filter_npoly = 3,
# Filtering IF data
ifdata_sigma = 1e-5,
# Analyzing data
analyze_iv = True,
analyze_if = True,
analyze = True, # DEPRECATED
# Junction properties
area = 1.5,
freq = None,
# Analyzing DC I-V curve
vgap_threshold = 105e-6,
vrn = (3.5e-3, 4.5e-3),
vrsg = 2e-3,
vleak = 2e-3,
# Analyzing DC IF data
vshot = None,
# Analyzing pumped I-V data (i.e., impedance recovery)
fit_range = (0.25, 0.8),
remb_range = (0, 1),
xemb_range = (-1, 1),
zemb = None,
alpha_max = 1.5,
num_b = 20,
# Analyzing pumped IF data (i.e., noise temperature analysis)
t_cold = 78.,
t_hot = 293.,
vbest = None,
best_pt = 'Max Gain',
# Import IF response data
ifresp_delimiter = '\t',
ifresp_usecols = (0, 1, 2),
ifresp_skipheader = 1,
ifresp_maxtn = 1e6,
# Response function
v_smear = 0.020,
# Plotting parameters
vmax_plot = 4.0,
# Miscellaneous
comment = '',
verbose = True,
)
"""Default parameters for importing experimental data."""
|
