Chemistry lib: readablility, lints, syntax, tests (#2202)

This change updates chemistry library:
- Removes old sysntax such as a! and [x, size=5]
- Reduced use of w/= where possible
- Makes long argument lists more readable
- Fixes error in comments
- Updates pairs of double representing a complex number to use complex
type
- Adds a few unit tests

No renames yet.

---------

Co-authored-by: Dmitry Vasilevsky <[email protected]>

Author: DmitryVasilevsky

library/chemistry/qsharp.json

@@ -23,6 +23,22 @@
     {
       "lint": "needlessParens",
       "level": "error"
+    },
+    {
+      "lint": "doubleEquality",
+      "level": "error"
+    },
+    {
+      "lint": "redundantSemicolons",
+      "level": "error"
+    },
+    {
+      "lint": "discourageChainAssignment",
+      "level": "error"
+    },
+    {
+      "lint": "needlessOperation",
+      "level": "error"
     }
   ],
   "files": [

library/chemistry/src/JordanWigner/Convenience.qs

@@ -6,18 +6,18 @@ export
     QubitizationOracle,
     OptimizedQubitizationOracle;
 
+import Std.Convert.IntAsDouble;
+import Std.Math.Ceiling;
+import Std.Math.Lg;
+
 import JordanWigner.JordanWignerBlockEncoding.JordanWignerBlockEncodingGeneratorSystem;
 import JordanWigner.JordanWignerEvolutionSet.JordanWignerFermionEvolutionSet;
 import JordanWigner.JordanWignerEvolutionSet.JordanWignerGeneratorSystem;
 import JordanWigner.JordanWignerOptimizedBlockEncoding.JordanWignerOptimizedBlockEncoding;
 import JordanWigner.JordanWignerOptimizedBlockEncoding.PauliBlockEncoding;
 import JordanWigner.JordanWignerOptimizedBlockEncoding.QuantumWalkByQubitization;
 import JordanWigner.Utils.JordanWignerEncodingData;
-import JordanWigner.Utils.MultiplexOperationsFromGenerator;
 import JordanWigner.Utils.TrotterSimulationAlgorithm;
-import Std.Convert.IntAsDouble;
-import Std.Math.Ceiling;
-import Std.Math.Lg;
 import Utils.EvolutionGenerator;
 
 // Convenience functions for performing simulation.
@@ -50,10 +50,9 @@ function TrotterStepOracle(jwHamiltonian : JordanWignerEncodingData, trotterStep
 
 function QubitizationOracleSeperatedRegisters(jwHamiltonian : JordanWignerEncodingData) : ((Int, Int), (Double, ((Qubit[], Qubit[]) => Unit is Adj + Ctl))) {
     let generatorSystem = JordanWignerBlockEncodingGeneratorSystem(jwHamiltonian.Terms);
-    let (nTerms, genIdxFunction) = generatorSystem!;
     let (oneNorm, blockEncodingReflection) = PauliBlockEncoding(generatorSystem);
     let nTargetRegisterQubits = jwHamiltonian.NumQubits;
-    let nCtrlRegisterQubits = Ceiling(Lg(IntAsDouble(nTerms)));
+    let nCtrlRegisterQubits = Ceiling(Lg(IntAsDouble(generatorSystem.NumEntries)));
     return ((nCtrlRegisterQubits, nTargetRegisterQubits), (oneNorm, QuantumWalkByQubitization(blockEncodingReflection)));
 }
 

library/chemistry/src/JordanWigner/ConvenienceVQE.qs

@@ -5,6 +5,8 @@ export
     EstimateEnergyWrapper,
     EstimateEnergy;
 
+import Std.Math.Complex;
+
 import JordanWigner.JordanWignerEvolutionSet.JordanWignerGeneratorSystem;
 import JordanWigner.JordanWignerVQE.EstimateTermExpectation;
 import JordanWigner.JordanWignerVQE.ExpandedCoefficients;
@@ -36,8 +38,8 @@ operation EstimateEnergyWrapper(jwHamiltonian : (Int, ((Int[], Double[])[], (Int
     let (inputState1, inputState2) = inputState;
     mutable jwInputState = [];
     for entry in inputState2 {
-        let (amp, idicies) = entry;
-        jwInputState += [new JordanWignerInputState { Amplitude = amp, FermionIndices = idicies }];
+        let ((r, i), idicies) = entry;
+        jwInputState += [new JordanWignerInputState { Amplitude = new Complex { Real = r, Imag = i }, FermionIndices = idicies }];
     }
     let inputState = (inputState1, jwInputState);
     let jwHamiltonian = new JordanWignerEncodingData {
@@ -67,26 +69,26 @@ operation EstimateEnergy(jwHamiltonian : JordanWignerEncodingData, nSamples : In
     // Initialize return value
     mutable energy = 0.;
 
-    // Unpack information and qubit Hamiltonian terms
-    let (nQubits, jwTerms, inputState, energyOffset) = jwHamiltonian!;
+    let nQubits = jwHamiltonian.NumQubits;
 
     // Loop over all qubit Hamiltonian terms
-    let (nTerms, indexFunction) = (JordanWignerGeneratorSystem(jwTerms))!;
+    let generatorSystem = JordanWignerGeneratorSystem(jwHamiltonian.Terms);
 
-    for idxTerm in 0..nTerms - 1 {
-        let term = indexFunction(idxTerm);
-        let ((idxTermType, coeff), idxFermions) = term!;
+    for idxTerm in 0..generatorSystem.NumEntries - 1 {
+        let term = generatorSystem.EntryAt(idxTerm);
+        let (idxTermType, coeff) = term.Term;
+        let idxFermions = term.Subsystem;
         let termType = idxTermType[0];
 
         let ops = MeasurementOperators(nQubits, idxFermions, termType);
         let coeffs = ExpandedCoefficients(coeff, termType);
 
         // The private wrapper enables fast emulation during expectation estimation
-        let inputStateUnitary = PrepareTrialState(inputState, _);
+        let inputStateUnitary = PrepareTrialState(jwHamiltonian.InputState, _);
 
         let jwTermEnergy = EstimateTermExpectation(inputStateUnitary, ops, coeffs, nQubits, nSamples);
         energy += jwTermEnergy;
     }
 
-    return energy + energyOffset;
+    return energy + jwHamiltonian.EnergyOffset;
 }

library/chemistry/src/JordanWigner/JordanWignerBlockEncoding.qs

@@ -3,9 +3,10 @@
 
 export JordanWignerBlockEncodingGeneratorSystem;
 
+import Std.Arrays.IndexRange;
+
 import JordanWigner.Utils.JWOptimizedHTerms;
 import JordanWigner.Utils.RangeAsIntArray;
-import Std.Arrays.IndexRange;
 import Utils.GeneratorIndex;
 import Utils.GeneratorSystem;
 import Utils.HTermToGenIdx;
@@ -164,7 +165,10 @@ function V0123TermToPauliGenIdx(term : GeneratorIndex) : GeneratorIndex[] {
 /// # Output
 /// Representation of Hamiltonian as `GeneratorSystem`.
 function JordanWignerBlockEncodingGeneratorSystem(data : JWOptimizedHTerms) : GeneratorSystem {
-    let (ZData, ZZData, PQandPQQRData, h0123Data) = data!;
+    let ZData = data.HTerm0;
+    let ZZData = data.HTerm1;
+    let PQandPQQRData = data.HTerm2;
+    let h0123Data = data.HTerm3;
     mutable genIdxes = Repeated(
         new GeneratorIndex { Term = ([0], [0.0]), Subsystem = [0] },
         ((Length(ZData) + Length(ZZData)) + 2 * Length(PQandPQQRData)) + 8 * Length(h0123Data)

library/chemistry/src/JordanWigner/JordanWignerClusterOperatorEvolutionSet.qs

@@ -5,10 +5,11 @@ export
     JordanWignerClusterOperatorEvolutionSet,
     JordanWignerClusterOperatorGeneratorSystem;
 
-import JordanWigner.Utils.JordanWignerInputState;
 import Std.Arrays.IndexRange;
 import Std.Math.Max;
 import Std.Math.Min;
+
+import JordanWigner.Utils.JordanWignerInputState;
 import Utils.GeneratorIndex;
 import Utils.GeneratorSystem;
 
@@ -28,19 +29,20 @@ import Utils.GeneratorSystem;
 ///
 /// # Example
 /// ```qsharp
-/// let bitString = ComputeJordanWignerBitString(6, [0,1,2,6]) ;
-/// // bitString is [false, false, false ,true, true, true, false].
+/// let bitString = ComputeJordanWignerBitString(5, [0, 3]) ;
+/// // bitString is [false, true, true, false, false].
 /// ```
 function ComputeJordanWignerBitString(nFermions : Int, idxFermions : Int[]) : Bool[] {
     if Length(idxFermions) % 2 != 0 {
         fail $"ComputeJordanWignerString failed. `idxFermions` must contain an even number of terms.";
     }
 
-    mutable zString = [false, size = nFermions];
+    mutable zString = Repeated(false, nFermions);
     for fermionIdx in idxFermions {
         if fermionIdx >= nFermions {
             fail $"ComputeJordanWignerString failed. fermionIdx {fermionIdx} out of range.";
         }
+        // NOTE: This could be optimized
         for idx in 0..fermionIdx {
             zString w/= idx <- not zString[idx];
         }
@@ -67,7 +69,12 @@ function ComputeJordanWignerPauliZString(nFermions : Int, idxFermions : Int[]) :
 
 // Identical to `ComputeJordanWignerPauliZString`, except that some
 // specified elements are substituted.
-function ComputeJordanWignerPauliString(nFermions : Int, idxFermions : Int[], pauliReplacements : Pauli[]) : Pauli[] {
+function ComputeJordanWignerPauliString(
+    nFermions : Int,
+    idxFermions : Int[],
+    pauliReplacements : Pauli[]
+) : Pauli[] {
+
     mutable pauliString = ComputeJordanWignerPauliZString(nFermions, idxFermions);
 
     for idx in IndexRange(idxFermions) {
@@ -89,8 +96,14 @@ function ComputeJordanWignerPauliString(nFermions : Int, idxFermions : Int[], pa
 /// Duration of time-evolution.
 /// ## qubits
 /// Qubits of Hamiltonian.
-operation ApplyJordanWignerClusterOperatorPQTerm(term : GeneratorIndex, stepSize : Double, qubits : Qubit[]) : Unit is Adj + Ctl {
-    let ((idxTermType, coeff), idxFermions) = term!;
+operation ApplyJordanWignerClusterOperatorPQTerm(
+    term : GeneratorIndex,
+    stepSize : Double,
+    qubits : Qubit[]
+) : Unit is Adj + Ctl {
+
+    let (_, coeff) = term.Term;
+    let idxFermions = term.Subsystem;
     let p = idxFermions[0];
     let q = idxFermions[1];
     if p == q {
@@ -117,8 +130,14 @@ operation ApplyJordanWignerClusterOperatorPQTerm(term : GeneratorIndex, stepSize
 /// Duration of time-evolution.
 /// ## qubits
 /// Qubits of Hamiltonian.
-operation ApplyJordanWignerClusterOperatorPQRSTerm(term : GeneratorIndex, stepSize : Double, qubits : Qubit[]) : Unit is Adj + Ctl {
-    let ((idxTermType, coeff), idxFermions) = term!;
+operation ApplyJordanWignerClusterOperatorPQRSTerm(
+    term : GeneratorIndex,
+    stepSize : Double,
+    qubits : Qubit[]
+) : Unit is Adj + Ctl {
+
+    let (_, coeff) = term.Term;
+    let idxFermions = term.Subsystem;
     let p = idxFermions[0];
     let q = idxFermions[1];
     let r = idxFermions[2];
@@ -146,8 +165,8 @@ function JordanWignerClusterOperatorPQRSTermSigns(indices : Int[]) : (Int[], Dou
     let q = indices[1];
     let r = indices[2];
     let s = indices[3];
-    mutable sorted = [0, size = 4];
-    mutable signs = [0.0, size = 8];
+    mutable sorted = [0, 0, 0, 0];
+    mutable signs = [0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0];
     mutable sign = 1.0;
 
     if (p > q) {
@@ -199,12 +218,18 @@ function JordanWignerClusterOperatorPQRSTermSigns(indices : Int[]) : (Int[], Dou
 ///
 /// # Output
 /// Representation of Hamiltonian as `GeneratorSystem`.
-function JordanWignerClusterOperatorGeneratorSystem(data : JordanWignerInputState[]) : GeneratorSystem {
-    new GeneratorSystem { NumEntries = Length(data), EntryAt = JordanWignerStateAsGeneratorIndex(data, _) }
+function JordanWignerClusterOperatorGeneratorSystem(
+    data : JordanWignerInputState[]
+) : GeneratorSystem {
+    new GeneratorSystem {
+        NumEntries = Length(data),
+        EntryAt = JordanWignerStateAsGeneratorIndex(data, _)
+    }
 }
 
 function JordanWignerStateAsGeneratorIndex(data : JordanWignerInputState[], idx : Int) : GeneratorIndex {
-    let ((real, imaginary), idxFermions) = data[idx]!;
+    let real = data[idx].Amplitude.Real;
+    let idxFermions = data[idx].FermionIndices;
 
     if Length(idxFermions) == 2 {
         // PQ term
@@ -229,8 +254,13 @@ function JordanWignerStateAsGeneratorIndex(data : JordanWignerInputState[], idx
 /// Dummy variable to match signature of simulation algorithms.
 /// ## qubits
 /// Register acted upon by time-evolution operator.
-operation JordanWignerClusterOperatorImpl(generatorIndex : GeneratorIndex, stepSize : Double, qubits : Qubit[]) : Unit is Adj + Ctl {
-    let ((idxTermType, idxDoubles), idxFermions) = generatorIndex!;
+operation JordanWignerClusterOperatorImpl(
+    generatorIndex : GeneratorIndex,
+    stepSize : Double,
+    qubits : Qubit[]
+) : Unit is Adj + Ctl {
+
+    let (idxTermType, _) = generatorIndex.Term;
     let termType = idxTermType[0];
 
     if termType == 0 {

library/chemistry/src/JordanWigner/JordanWignerEvolutionSet.qs

@@ -5,9 +5,10 @@ export
     JordanWignerGeneratorSystem,
     JordanWignerFermionEvolutionSet;
 
-import JordanWigner.Utils.JWOptimizedHTerms;
 import Std.Arrays.IndexRange;
 import Std.Arrays.Subarray;
+
+import JordanWigner.Utils.JWOptimizedHTerms;
 import Utils.GeneratorIndex;
 import Utils.GeneratorSystem;
 import Utils.HTermsToGenSys;
@@ -77,7 +78,8 @@ operation ApplyJordanWignerZZTerm(term : GeneratorIndex, stepSize : Double, qubi
 /// ## qubits
 /// Qubits of Hamiltonian.
 operation ApplyJordanWignerPQTerm(term : GeneratorIndex, stepSize : Double, extraParityQubits : Qubit[], qubits : Qubit[]) : Unit is Adj + Ctl {
-    let ((idxTermType, coeff), idxFermions) = term!;
+    let (_, coeff) = term.Term;
+    let idxFermions = term.Subsystem;
     let angle = (1.0 * coeff[0]) * stepSize;
     let qubitsPQ = Subarray(idxFermions[0..1], qubits);
     let qubitsJW = qubits[idxFermions[0] + 1..idxFermions[1] - 1];
@@ -101,7 +103,8 @@ operation ApplyJordanWignerPQTerm(term : GeneratorIndex, stepSize : Double, extr
 /// ## qubits
 /// Qubits of Hamiltonian.
 operation ApplyJordanWignerPQandPQQRTerm(term : GeneratorIndex, stepSize : Double, qubits : Qubit[]) : Unit is Adj + Ctl {
-    let ((idxTermType, coeff), idxFermions) = term!;
+    let (idxTermType, coeff) = term.Term;
+    let idxFermions = term.Subsystem;
     let angle = (1.0 * coeff[0]) * stepSize;
     let qubitQidx = idxFermions[1];
 
@@ -138,7 +141,8 @@ operation ApplyJordanWignerPQandPQQRTerm(term : GeneratorIndex, stepSize : Doubl
 /// ## qubits
 /// Qubits to apply the given term to.
 operation ApplyJordanWigner0123Term(term : GeneratorIndex, stepSize : Double, qubits : Qubit[]) : Unit is Adj + Ctl {
-    let ((idxTermType, v0123), idxFermions) = term!;
+    let (idxTermType, v0123) = term.Term;
+    let idxFermions = term.Subsystem;
     let angle = stepSize;
     let qubitsPQ = Subarray(idxFermions[0..1], qubits);
     let qubitsRS = Subarray(idxFermions[2..3], qubits);
@@ -166,7 +170,10 @@ operation ApplyJordanWigner0123Term(term : GeneratorIndex, stepSize : Double, qu
 /// # Output
 /// Representation of Hamiltonian as `GeneratorSystem`.
 function JordanWignerGeneratorSystem(data : JWOptimizedHTerms) : GeneratorSystem {
-    let (ZData, ZZData, PQandPQQRData, h0123Data) = data!;
+    let ZData = data.HTerm0;
+    let ZZData = data.HTerm1;
+    let PQandPQQRData = data.HTerm2;
+    let h0123Data = data.HTerm3;
     let ZGenSys = HTermsToGenSys(ZData, [0]);
     let ZZGenSys = HTermsToGenSys(ZZData, [1]);
     let PQandPQQRGenSys = HTermsToGenSys(PQandPQQRData, [2]);
@@ -214,7 +221,7 @@ function AddGeneratorSystems(generatorSystemA : GeneratorSystem, generatorSystem
 /// ## qubits
 /// Register acted upon by time-evolution operator.
 operation JordanWignerFermionImpl(generatorIndex : GeneratorIndex, stepSize : Double, qubits : Qubit[]) : Unit is Adj + Ctl {
-    let ((idxTermType, idxDoubles), idxFermions) = generatorIndex!;
+    let (idxTermType, idxDoubles) = generatorIndex.Term;
     let termType = idxTermType[0];
 
     if (termType == 0) {