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Cleanup docs/noise.ipynb in preparation for Cirq 1.0 launch #5147

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Mar 25, 2022
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Cleanup docs/noise.ipynb in preparation for Cirq 1.0 launch #5147

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31 changes: 16 additions & 15 deletions docs/noise.ipynb
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Original file line number Diff line number Diff line change
Expand Up @@ -116,7 +116,7 @@
"id": "708b5b720a74"
},
"source": [
"Cirq defines many commonly used quantum channels in [`ops/common_channels.py`](https://github.com/quantumlib/Cirq/blob/master/cirq/ops/common_channels.py). For example, the single-qubit bit-flip channel\n",
"Cirq defines many commonly used quantum channels in [`ops/common_channels.py`](https://github.com/quantumlib/Cirq/blob/master/cirq-core/cirq/ops/common_channels.py). For example, the single-qubit bit-flip channel\n",
"\n",
"$$\n",
"\\rho \\rightarrow (1 - p) \\rho + p X \\rho X\n",
Expand Down Expand Up @@ -145,7 +145,7 @@
"id": "f1f501177e53"
},
"source": [
"To see the Kraus operators of a channel, the `cirq.channel` protocol can be used. (See the [protocols guide](./protocols.ipynb).)"
"To see the Kraus operators of a channel, the `cirq.kraus` protocol can be used. (See the [protocols guide](./protocols.ipynb).)"
]
},
{
Expand Down Expand Up @@ -282,7 +282,7 @@
"id": "ddbc622c98da"
},
"source": [
"## The `channel` and `mixture` protocols"
"## The `kraus` and `mixture` protocols"
]
},
{
Expand All @@ -291,7 +291,7 @@
"id": "2dee355d2ae8"
},
"source": [
"We have seen the `cirq.channel` protocol which returns the Kraus operators of a channel. Some channels have the interpretation of randomly applying a single unitary Kraus operator $U_k$ with probability $p_k$, namely\n",
"We have seen the `cirq.kraus` protocol which returns the Kraus operators of a channel. Some channels have the interpretation of randomly applying a single unitary Kraus operator $U_k$ with probability $p_k$, namely\n",
"\n",
"$$\n",
"\\rho \\rightarrow \\sum_k p_k U_k \\rho U_k^\\dagger {\\rm ~where~} \\sum_k p_k =1 {\\rm ~and~ U_k U_k^\\dagger= I}.\n",
Expand Down Expand Up @@ -361,9 +361,9 @@
"source": [
"To summarize:\n",
"\n",
"* Every `Gate` in Cirq supports the `cirq.channel` protocol.\n",
" - If magic method `_kraus_` is not defined, `cirq.channel` looks for `_mixture_` then for `_unitary_`.\n",
"* A subset of channels which support `cirq.channel` also support the `cirq.mixture` protocol.\n",
"* Every `Gate` in Cirq supports the `cirq.kraus` protocol.\n",
" - If magic method `_kraus_` is not defined, `cirq.kraus` looks for `_mixture_` then for `_unitary_`.\n",
"* A subset of channels which support `cirq.kraus` also support the `cirq.mixture` protocol.\n",
" - If magic method `_mixture_` is not defined, `cirq.mixture` looks for `_unitary_`.\n",
"* A subset of channels which support `cirq.mixture` also support the `cirq.unitary` protocol."
]
Expand All @@ -377,11 +377,11 @@
"For concrete examples, consider `cirq.X`, `cirq.BitFlipChannel`, and `cirq.AmplitudeDampingChannel` which are all subclasses of `cirq.Gate`.\n",
"\n",
"* `cirq.X` defines the `_unitary_` method. \n",
" - As a result, it supports the `cirq.unitary` protocol, the `cirq.mixture` protocol, and the `cirq.channel` protocol.\n",
" - As a result, it supports the `cirq.unitary` protocol, the `cirq.mixture` protocol, and the `cirq.kraus` protocol.\n",
"* `cirq.BitFlipChannel` defines the `_mixture_` method but not the `_unitary_` method.\n",
" - As a result, it only supports the `cirq.mixture` protocol and the `cirq.channel` protocol.\n",
" - As a result, it only supports the `cirq.mixture` protocol and the `cirq.kraus` protocol.\n",
"* `cirq.AmplitudeDampingChannel` defines the `_kraus_` method, but not the `_mixture_` method or the `_unitary_` method.\n",
" - As a result, it only supports the `cirq.channel` protocol."
" - As a result, it only supports the `cirq.kraus` protocol."
]
},
{
Expand Down Expand Up @@ -425,7 +425,7 @@
" (0.9, np.array([[1, 0], [0, 1]], dtype=np.complex64)),\n",
" (0.1, np.array([[0, 1], [1, 0]], dtype=np.complex64)),\n",
"]\n",
"bit_flip = cirq.MixedUnitaryChannel(mix)\n",
"bit_flip_mix = cirq.MixedUnitaryChannel(mix)\n",
"\n",
"# This is equivalent to an X-basis measurement.\n",
"ops = [\n",
Expand All @@ -436,7 +436,7 @@
"\n",
"# These circuits have the same behavior.\n",
"circuit = cirq.Circuit(\n",
" bit_flip.on(q0),\n",
" bit_flip_mix.on(q0),\n",
" cirq.H(q0),\n",
" x_meas.on(q0),\n",
")\n",
Expand Down Expand Up @@ -531,7 +531,7 @@
"id": "72486a155131"
},
"source": [
"Note: Since `_mixture_` is defined, the `cirq.channel` protocol can also be used."
"Note: Since `_mixture_` is defined, the `cirq.kraus` protocol can also be used."
]
},
{
Expand Down Expand Up @@ -890,7 +890,7 @@
"id": "11b18c640767"
},
"source": [
"Another technique is to pass a noise channel to the density matrix simulator as shown below."
"Another technique is to directly pass a `cirq.NoiseModel`, or a value that can be trivially converted into one, to the density matrix simulator as shown below."
]
},
{
Expand All @@ -901,7 +901,8 @@
},
"outputs": [],
"source": [
"\"\"\"Define a density matrix simulator with a noise model.\"\"\"\n",
"\"\"\"Define a density matrix simulator with a `cirq.NOISE_MODEL_LIKE` object.\"\"\"\n",
"\n",
"noisy_dsim = cirq.DensityMatrixSimulator(\n",
" noise=cirq.generalized_amplitude_damp(p=0.1, gamma=0.5)\n",
")"
Expand Down