Feature request: classical registers #887
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area/classical/data
area/classical
kind/feature-request
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My understanding is that there was a conscious design decision to not support this because current hardware can't do intermediate measurements. |
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@bryano is correct. We don't know what the limitations of feedforward will actually be, so for now we've avoided codifying it. The closest thing we have to any kind of classical processing at the moment is the invert-result mask on measurement gates. |
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Reopening based on comments by @balopat. |
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Related #3231. |
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This was referenced Dec 24, 2021
CirqBot
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Adds a `ClassicalDataStore` class so we can keep track of which qubits are associated to which measurements. Closes #3232. Initially this was created as part 14 (of 14) of https://tinyurl.com/cirq-feedforward to enable qudits in classical conditions, by storing and using dimensions of the measured qubits when calculating the integer value of each measurement when resolving sympy expressions. However it may have broader applicability. This approach also sets us up to more easily add different types of measurements (#3233, #4274). It will also ease the path to #3002 and #4449., as we can eventually pass this into `Result` rather than the raw `log_of_measurement_results` dictionary. (The return type of `_run` will have to be changed to `Sequence[C;assicalDataStoreReader]`. Related: #887, #3231 (open question @95-martin-orion whether this closes those or not) This PR contains a `ClassicalDataStoreReader` and `ClassicalDataStoreBase` parent "interface" for the `ClassicalDataStore` class as well. This will allow us to swap in different representations that may have different performance characteristics. See #3808 for an example use case. This could be done by adding an optional `ClassicalDataStore` factory method argument to the `SimulatorBase` initializer, or separately to sampler classes. (Note this is an alternative to #4778 for supporting qudits in sympy classical control expressions, as discussed here: https://github.com/quantumlib/Cirq/pull/4778/files#r774816995. The other PR was simpler and less invasive, but a bit hacky. I felt even though bigger, this seemed like the better approach and especially fits better with our future direction, and closed the other one). **Breaking Changes**: 1. The abstract method `SimulatorBase._create_partial_act_on_args` argument `log_of_measurement_results: Dict` has been changed to `classical_data: ClassicalData`. Any third-party simulators that inherit `SimulatorBase` will need to update their implementation accordingly. 2. The abstract base class `ActOnArgs.__init__` argument `log_of_measurement_results: Dict` is now copied before use. For users that depend on the pass-by-reference semantics (this should be rare), they can use the new `classical_data: ClassicalData` argument instead, which is pass-by-reference.
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@vtomole I think all the work in classical controls means this can be closed. |
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…mlib#4781) Adds a `ClassicalDataStore` class so we can keep track of which qubits are associated to which measurements. Closes quantumlib#3232. Initially this was created as part 14 (of 14) of https://tinyurl.com/cirq-feedforward to enable qudits in classical conditions, by storing and using dimensions of the measured qubits when calculating the integer value of each measurement when resolving sympy expressions. However it may have broader applicability. This approach also sets us up to more easily add different types of measurements (quantumlib#3233, quantumlib#4274). It will also ease the path to quantumlib#3002 and quantumlib#4449., as we can eventually pass this into `Result` rather than the raw `log_of_measurement_results` dictionary. (The return type of `_run` will have to be changed to `Sequence[C;assicalDataStoreReader]`. Related: quantumlib#887, quantumlib#3231 (open question @95-martin-orion whether this closes those or not) This PR contains a `ClassicalDataStoreReader` and `ClassicalDataStoreBase` parent "interface" for the `ClassicalDataStore` class as well. This will allow us to swap in different representations that may have different performance characteristics. See quantumlib#3808 for an example use case. This could be done by adding an optional `ClassicalDataStore` factory method argument to the `SimulatorBase` initializer, or separately to sampler classes. (Note this is an alternative to quantumlib#4778 for supporting qudits in sympy classical control expressions, as discussed here: https://github.com/quantumlib/Cirq/pull/4778/files#r774816995. The other PR was simpler and less invasive, but a bit hacky. I felt even though bigger, this seemed like the better approach and especially fits better with our future direction, and closed the other one). **Breaking Changes**: 1. The abstract method `SimulatorBase._create_partial_act_on_args` argument `log_of_measurement_results: Dict` has been changed to `classical_data: ClassicalData`. Any third-party simulators that inherit `SimulatorBase` will need to update their implementation accordingly. 2. The abstract base class `ActOnArgs.__init__` argument `log_of_measurement_results: Dict` is now copied before use. For users that depend on the pass-by-reference semantics (this should be rare), they can use the new `classical_data: ClassicalData` argument instead, which is pass-by-reference.
harry-phasecraft
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…mlib#4781) Adds a `ClassicalDataStore` class so we can keep track of which qubits are associated to which measurements. Closes quantumlib#3232. Initially this was created as part 14 (of 14) of https://tinyurl.com/cirq-feedforward to enable qudits in classical conditions, by storing and using dimensions of the measured qubits when calculating the integer value of each measurement when resolving sympy expressions. However it may have broader applicability. This approach also sets us up to more easily add different types of measurements (quantumlib#3233, quantumlib#4274). It will also ease the path to quantumlib#3002 and quantumlib#4449., as we can eventually pass this into `Result` rather than the raw `log_of_measurement_results` dictionary. (The return type of `_run` will have to be changed to `Sequence[C;assicalDataStoreReader]`. Related: quantumlib#887, quantumlib#3231 (open question @95-martin-orion whether this closes those or not) This PR contains a `ClassicalDataStoreReader` and `ClassicalDataStoreBase` parent "interface" for the `ClassicalDataStore` class as well. This will allow us to swap in different representations that may have different performance characteristics. See quantumlib#3808 for an example use case. This could be done by adding an optional `ClassicalDataStore` factory method argument to the `SimulatorBase` initializer, or separately to sampler classes. (Note this is an alternative to quantumlib#4778 for supporting qudits in sympy classical control expressions, as discussed here: https://github.com/quantumlib/Cirq/pull/4778/files#r774816995. The other PR was simpler and less invasive, but a bit hacky. I felt even though bigger, this seemed like the better approach and especially fits better with our future direction, and closed the other one). **Breaking Changes**: 1. The abstract method `SimulatorBase._create_partial_act_on_args` argument `log_of_measurement_results: Dict` has been changed to `classical_data: ClassicalData`. Any third-party simulators that inherit `SimulatorBase` will need to update their implementation accordingly. 2. The abstract base class `ActOnArgs.__init__` argument `log_of_measurement_results: Dict` is now copied before use. For users that depend on the pass-by-reference semantics (this should be rare), they can use the new `classical_data: ClassicalData` argument instead, which is pass-by-reference.
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Intermediate representations like QASM have
creg c0[1];to initialize classical registers andmeasure q[0] -> c0[0];for assigning measurement results to classical memory. Are there equivalent procedures in Cirq?The text was updated successfully, but these errors were encountered: